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llvm-project/llvm/test/CodeGen/X86/sdiv-exact.ll

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[SDAG] Now that we have a way to communicate the exact bit on sdiv use it to simplify sdiv by a constant. We had a hack in SDAGBuilder in place to work around this but now we can avoid that. Call BuildExactSDIV from BuildSDIV so DAGCombiner can perform this trick automatically. The added check in DAGCombiner is necessary to prevent exact sdiv by pow2 from regressing as the target-specific pow2 lowering is not aware of exact bits yet. This is mostly covered by existing tests. One side effect is that we get the better lowering for exact vector sdivs now too :) llvm-svn: 240891
2015-06-28 04:33:26 +08:00
; RUN: llc -march=x86 -mattr=+sse2 < %s | FileCheck %s
Emit a more efficient magic number multiplication for exact sdivs. 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
2011-07-08 18:31:30 +08:00
define i32 @test1(i32 %x) {
%div = sdiv exact i32 %x, 25
ret i32 %div
Convert CodeGen/*/*.ll tests to use the new CHECK-LABEL for easier debugging. No functionality change and all tests pass after conversion. This was done with the following sed invocation to catch label lines demarking function boundaries: sed -i '' "s/^;\( *\)\([A-Z0-9_]*\):\( *\)test\([A-Za-z0-9_-]*\):\( *\)$/;\1\2-LABEL:\3test\4:\5/g" test/CodeGen/*/*.ll which was written conservatively to avoid false positives rather than false negatives. I scanned through all the changes and everything looks correct. llvm-svn: 186258
2013-07-14 04:38:47 +08:00
; CHECK-LABEL: test1:
Emit a more efficient magic number multiplication for exact sdivs. 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
2011-07-08 18:31:30 +08:00
; CHECK: imull $-1030792151, 4(%esp)
; CHECK-NEXT: ret
}
define i32 @test2(i32 %x) {
%div = sdiv exact i32 %x, 24
ret i32 %div
Convert CodeGen/*/*.ll tests to use the new CHECK-LABEL for easier debugging. No functionality change and all tests pass after conversion. This was done with the following sed invocation to catch label lines demarking function boundaries: sed -i '' "s/^;\( *\)\([A-Z0-9_]*\):\( *\)test\([A-Za-z0-9_-]*\):\( *\)$/;\1\2-LABEL:\3test\4:\5/g" test/CodeGen/*/*.ll which was written conservatively to avoid false positives rather than false negatives. I scanned through all the changes and everything looks correct. llvm-svn: 186258
2013-07-14 04:38:47 +08:00
; CHECK-LABEL: test2:
Emit a more efficient magic number multiplication for exact sdivs. 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
2011-07-08 18:31:30 +08:00
; CHECK: sarl $3
; CHECK-NEXT: imull $-1431655765
; CHECK-NEXT: ret
}
[SDAG] Now that we have a way to communicate the exact bit on sdiv use it to simplify sdiv by a constant. We had a hack in SDAGBuilder in place to work around this but now we can avoid that. Call BuildExactSDIV from BuildSDIV so DAGCombiner can perform this trick automatically. The added check in DAGCombiner is necessary to prevent exact sdiv by pow2 from regressing as the target-specific pow2 lowering is not aware of exact bits yet. This is mostly covered by existing tests. One side effect is that we get the better lowering for exact vector sdivs now too :) llvm-svn: 240891
2015-06-28 04:33:26 +08:00
define <4 x i32> @test3(<4 x i32> %x) {
%div = sdiv exact <4 x i32> %x, <i32 24, i32 24, i32 24, i32 24>
ret <4 x i32> %div
; CHECK-LABEL: test3:
; CHECK: psrad $3,
; CHECK: pmuludq
; CHECK: pmuludq
; CHECK-NOT: psrad
; CHECK: ret
}