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7eae8125c6
Current findBestLoopTop can find and move one kind of block to top, a latch block has one successor. Another common case is:
* a latch block
* it has two successors, one is loop header, another is exit
* it has more than one predecessors
If it is below one of its predecessors P, only P can fall through to it, all other predecessors need a jump to it, and another conditional jump to loop header. If it is moved before loop header, all its predecessors jump to it, then fall through to loop header. So all its predecessors except P can reduce one taken branch.
Differential Revision: https://reviews.llvm.org/D43256
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@363471 91177308-0d34-0410-b5e6-96231b3b80d8
166 lines
5.7 KiB
LLVM
166 lines
5.7 KiB
LLVM
; RUN: llc < %s -mtriple=powerpc64le-unknown-linux-gnu -verify-machineinstrs -mcpu=pwr8 | FileCheck %s --check-prefixes=CHECK,CHECK-PWR8
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; RUN: llc < %s -mtriple=powerpc64le-unknown-linux-gnu -verify-machineinstrs -mcpu=a2q | FileCheck %s --check-prefixes=CHECK,CHECK-A2Q
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; Verify that we do NOT generate the mtctr instruction for loop trip counts < 4
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; The latency of the mtctr is only justified if there are more than 4 comparisons that are removed as a result.
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@a = common local_unnamed_addr global i32 0, align 4
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@b = common local_unnamed_addr global i32 0, align 4
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@c = common local_unnamed_addr global i32 0, align 4
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@d = common local_unnamed_addr global i32 0, align 4
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@e = common local_unnamed_addr global i32 0, align 4
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@f = common local_unnamed_addr global i32 0, align 4
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@arr = common local_unnamed_addr global [5 x i32] zeroinitializer, align 4
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; Function Attrs: norecurse nounwind readonly
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define signext i32 @testTripCount2(i32 signext %a) {
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; CHECK-LABEL: testTripCount2:
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; CHECK-NOT: mtctr
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; CHECK: blr
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entry:
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br label %for.body
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for.cond.cleanup: ; preds = %for.body
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ret i32 %add
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for.body: ; preds = %entry, %for.body
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%indvars.iv = phi i64 [ 1, %entry ], [ %indvars.iv.next, %for.body ]
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%Sum.05 = phi i32 [ 0, %entry ], [ %add, %for.body ]
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%arrayidx = getelementptr inbounds [5 x i32], [5 x i32]* @arr, i64 0, i64 %indvars.iv
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%0 = load i32, i32* %arrayidx, align 4
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%add = add nsw i32 %0, %Sum.05
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%indvars.iv.next = add nsw i64 %indvars.iv, -1
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%tobool = icmp eq i64 %indvars.iv, 0
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br i1 %tobool, label %for.cond.cleanup, label %for.body
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}
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; Function Attrs: norecurse nounwind readonly
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define signext i32 @testTripCount3(i32 signext %a) {
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; CHECK-LABEL: testTripCount3:
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; CHECK-NOT: mtctr
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; CHECK: blr
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entry:
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br label %for.body
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for.cond.cleanup: ; preds = %for.body
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ret i32 %add
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for.body: ; preds = %entry, %for.body
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%indvars.iv = phi i64 [ 2, %entry ], [ %indvars.iv.next, %for.body ]
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%Sum.05 = phi i32 [ 0, %entry ], [ %add, %for.body ]
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%arrayidx = getelementptr inbounds [5 x i32], [5 x i32]* @arr, i64 0, i64 %indvars.iv
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%0 = load i32, i32* %arrayidx, align 4
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%add = add nsw i32 %0, %Sum.05
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%indvars.iv.next = add nsw i64 %indvars.iv, -1
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%tobool = icmp eq i64 %indvars.iv, 0
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br i1 %tobool, label %for.cond.cleanup, label %for.body
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}
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; Function Attrs: norecurse nounwind readonly
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define signext i32 @testTripCount4(i32 signext %a) {
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; CHECK-LABEL: testTripCount4:
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; CHECK: mtctr
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; CHECK: bdnz
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entry:
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br label %for.body
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for.cond.cleanup: ; preds = %for.body
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ret i32 %add
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for.body: ; preds = %entry, %for.body
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%indvars.iv = phi i64 [ 3, %entry ], [ %indvars.iv.next, %for.body ]
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%Sum.05 = phi i32 [ 0, %entry ], [ %add, %for.body ]
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%arrayidx = getelementptr inbounds [5 x i32], [5 x i32]* @arr, i64 0, i64 %indvars.iv
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%0 = load i32, i32* %arrayidx, align 4
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%add = add nsw i32 %0, %Sum.05
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%indvars.iv.next = add nsw i64 %indvars.iv, -1
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%tobool = icmp eq i64 %indvars.iv, 0
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br i1 %tobool, label %for.cond.cleanup, label %for.body
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}
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; Function Attrs: norecurse nounwind
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define signext i32 @testTripCount2NonSmallLoop() {
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; CHECK-LABEL: testTripCount2NonSmallLoop:
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; CHECK: blt
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; CHECK: beq
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; CHECK: blr
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entry:
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%.pre = load i32, i32* @a, align 4
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br label %for.body
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for.body: ; preds = %entry, %if.end
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%0 = phi i32 [ %.pre, %entry ], [ %1, %if.end ]
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%dec4 = phi i32 [ 1, %entry ], [ %dec, %if.end ]
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%b.03 = phi i8 [ 0, %entry ], [ %b.1, %if.end ]
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%tobool1 = icmp eq i32 %0, 0
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br i1 %tobool1, label %if.end, label %if.then
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if.then: ; preds = %for.body
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store i32 2, i32* @a, align 4
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br label %if.end
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if.end: ; preds = %for.body, %if.then
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%1 = phi i32 [ 2, %if.then ], [ 0, %for.body ]
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%b.1 = phi i8 [ 2, %if.then ], [ %b.03, %for.body ]
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%dec = add nsw i32 %dec4, -1
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%tobool = icmp eq i32 %dec4, 0
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br i1 %tobool, label %for.end, label %for.body
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for.end: ; preds = %if.end
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%conv = zext i8 %b.1 to i32
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ret i32 %conv
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}
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; On core a2q, IssueWidth is 1. On core pwr8, IssueWidth is 8.
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; a2q should use mtctr, but pwr8 should not use mtctr.
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define signext i32 @testTripCount5() {
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; CHECK-LABEL: testTripCount5:
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; CHECK-PWR8-NOT: mtctr
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; CHECK-A2Q: mtctr
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entry:
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%.prea = load i32, i32* @a, align 4
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%.preb = load i32, i32* @b, align 4
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%.prec = load i32, i32* @c, align 4
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%.pred = load i32, i32* @d, align 4
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%.pree = load i32, i32* @e, align 4
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%.pref = load i32, i32* @f, align 4
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br label %for.body
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for.body: ; preds = %entry, %for.body
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%indvars.iv = phi i64 [ 2, %entry ], [ %indvars.iv.next, %for.body ]
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%0 = phi i32 [ %.prea, %entry ], [ %6, %for.body ]
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%1 = phi i32 [ %.preb, %entry ], [ %7, %for.body ]
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%2 = phi i32 [ %.prec, %entry ], [ %8, %for.body ]
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%3 = phi i32 [ %.pred, %entry ], [ %9, %for.body ]
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%4 = phi i32 [ %.pree, %entry ], [ %10, %for.body ]
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%5 = phi i32 [ %.pref, %entry ], [ %11, %for.body ]
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%6 = add i32 %0, 1
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%7 = add i32 %1, 1
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%8 = add i32 %2, 1
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%9 = add i32 %3, 1
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%10 = add i32 %4, 1
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%11 = add i32 %5, 1
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%indvars.iv.next = add nsw i64 %indvars.iv, -1
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%tobool = icmp eq i64 %indvars.iv, 0
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br i1 %tobool, label %for.end, label %for.body
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for.end: ; preds = %for.body
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store i32 %6, i32* @a, align 4
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store i32 %7, i32* @b, align 4
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store i32 %8, i32* @c, align 4
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store i32 %9, i32* @d, align 4
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store i32 %10, i32* @e, align 4
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store i32 %11, i32* @f, align 4
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ret i32 0
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}
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