llvm/test/CodeGen/X86/shift-folding.ll
Chandler Carruth 62dfc51152 Prevent a DAGCombine from firing where there are two uses of
a combined-away node and the result of the combine isn't substantially
smaller than the input, it's just canonicalized. This is the first part
of a significant (7%) performance gain for Snappy's hot decompression
loop.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147604 91177308-0d34-0410-b5e6-96231b3b80d8
2012-01-05 11:05:55 +00:00

71 lines
1.4 KiB
LLVM

; RUN: llc < %s -march=x86 | FileCheck %s
define i32* @test1(i32* %P, i32 %X) {
; CHECK: test1:
; CHECK-NOT: shrl
; CHECK-NOT: shll
; CHECK: ret
entry:
%Y = lshr i32 %X, 2
%gep.upgrd.1 = zext i32 %Y to i64
%P2 = getelementptr i32* %P, i64 %gep.upgrd.1
ret i32* %P2
}
define i32* @test2(i32* %P, i32 %X) {
; CHECK: test2:
; CHECK: shll $4
; CHECK-NOT: shll
; CHECK: ret
entry:
%Y = shl i32 %X, 2
%gep.upgrd.2 = zext i32 %Y to i64
%P2 = getelementptr i32* %P, i64 %gep.upgrd.2
ret i32* %P2
}
define i32* @test3(i32* %P, i32 %X) {
; CHECK: test3:
; CHECK-NOT: shrl
; CHECK-NOT: shll
; CHECK: ret
entry:
%Y = ashr i32 %X, 2
%P2 = getelementptr i32* %P, i32 %Y
ret i32* %P2
}
define fastcc i32 @test4(i32* %d) {
; CHECK: test4:
; CHECK-NOT: shrl
; CHECK: ret
entry:
%tmp4 = load i32* %d
%tmp512 = lshr i32 %tmp4, 24
ret i32 %tmp512
}
define i64 @test5(i16 %i, i32* %arr) {
; Ensure that we don't fold away shifts which have multiple uses, as they are
; just re-introduced for the second use.
; CHECK: test5:
; CHECK-NOT: shrl
; CHECK: shrl $11
; CHECK-NOT: shrl
; CHECK: ret
entry:
%i.zext = zext i16 %i to i32
%index = lshr i32 %i.zext, 11
%index.zext = zext i32 %index to i64
%val.ptr = getelementptr inbounds i32* %arr, i64 %index.zext
%val = load i32* %val.ptr
%val.zext = zext i32 %val to i64
%sum = add i64 %val.zext, %index.zext
ret i64 %sum
}