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44c76d239a
We have to do this in DAGBuilder instead of DAGCombiner, because the exact bit is lost after building.
struct foo { char x[24]; };
long bar(struct foo *a, struct foo *b) { return a-b; }
is now compiled into
movl 4(%esp), %eax
subl 8(%esp), %eax
sarl $3, %eax
imull $-1431655765, %eax, %eax
instead of
movl 4(%esp), %eax
subl 8(%esp), %eax
movl $715827883, %ecx
imull %ecx
movl %edx, %eax
shrl $31, %eax
sarl $2, %edx
addl %eax, %edx
movl %edx, %eax
llvm-svn: 134695
19 lines
351 B
LLVM
19 lines
351 B
LLVM
; RUN: llc -march=x86 < %s | FileCheck %s
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define i32 @test1(i32 %x) {
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%div = sdiv exact i32 %x, 25
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ret i32 %div
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; CHECK: test1:
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; CHECK: imull $-1030792151, 4(%esp)
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; CHECK-NEXT: ret
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}
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define i32 @test2(i32 %x) {
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%div = sdiv exact i32 %x, 24
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ret i32 %div
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; CHECK: test2:
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; CHECK: sarl $3
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; CHECK-NEXT: imull $-1431655765
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; CHECK-NEXT: ret
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}
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