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The ARM backend can eliminate cmp instructions by reusing flags from a nearby sub instruction with similar arguments. Don't do that if the sub is predicated - the flags are not written unconditionally. <rdar://problem/12263428> git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163535 91177308-0d34-0410-b5e6-96231b3b80d8
87 lines
1.9 KiB
LLVM
87 lines
1.9 KiB
LLVM
; RUN: llc < %s -mtriple=arm-apple-darwin | FileCheck %s
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define i32 @f(i32 %a, i32 %b) nounwind ssp {
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entry:
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; CHECK: f:
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; CHECK: subs
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; CHECK-NOT: cmp
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%cmp = icmp sgt i32 %a, %b
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%sub = sub nsw i32 %a, %b
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%sub. = select i1 %cmp, i32 %sub, i32 0
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ret i32 %sub.
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}
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define i32 @g(i32 %a, i32 %b) nounwind ssp {
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entry:
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; CHECK: g:
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; CHECK: subs
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; CHECK-NOT: cmp
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%cmp = icmp slt i32 %a, %b
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%sub = sub nsw i32 %b, %a
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%sub. = select i1 %cmp, i32 %sub, i32 0
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ret i32 %sub.
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}
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define i32 @h(i32 %a, i32 %b) nounwind ssp {
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entry:
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; CHECK: h:
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; CHECK: subs
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; CHECK-NOT: cmp
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%cmp = icmp sgt i32 %a, 3
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%sub = sub nsw i32 %a, 3
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%sub. = select i1 %cmp, i32 %sub, i32 %b
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ret i32 %sub.
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}
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; rdar://11725965
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define i32 @i(i32 %a, i32 %b) nounwind readnone ssp {
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entry:
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; CHECK: i:
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; CHECK: subs
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; CHECK-NOT: cmp
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%cmp = icmp ult i32 %a, %b
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%sub = sub i32 %b, %a
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%sub. = select i1 %cmp, i32 %sub, i32 0
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ret i32 %sub.
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}
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; If CPSR is live-out, we can't remove cmp if there exists
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; a swapped sub.
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define i32 @j(i32 %a, i32 %b) nounwind {
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entry:
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; CHECK: j:
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; CHECK: sub
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; CHECK: cmp
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%cmp = icmp eq i32 %b, %a
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%sub = sub nsw i32 %a, %b
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br i1 %cmp, label %if.then, label %if.else
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if.then:
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%cmp2 = icmp sgt i32 %b, %a
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%sel = select i1 %cmp2, i32 %sub, i32 %a
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ret i32 %sel
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if.else:
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ret i32 %sub
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}
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; If the sub/rsb instruction is predicated, we can't use the flags.
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; <rdar://problem/12263428>
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; Test case from MultiSource/Benchmarks/Ptrdist/bc/number.s
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; CHECK: bc_raise
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; CHECK: rsbeq
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; CHECK: cmp
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define i32 @bc_raise() nounwind ssp {
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entry:
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%val.2.i = select i1 undef, i32 0, i32 undef
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%sub.i = sub nsw i32 0, %val.2.i
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%retval.0.i = select i1 undef, i32 %val.2.i, i32 %sub.i
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%cmp1 = icmp eq i32 %retval.0.i, 0
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br i1 %cmp1, label %land.lhs.true, label %if.end11
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land.lhs.true: ; preds = %num2long.exit
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ret i32 17
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if.end11: ; preds = %num2long.exit
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ret i32 23
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}
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