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| author | Guozhi Wei <carrot@google.com> | 2019-01-31 20:46:42 +0000 |
|---|---|---|
| committer | Guozhi Wei <carrot@google.com> | 2019-01-31 20:46:42 +0000 |
| commit | 0bed9e0453e1298f4323a3ec5d94a6e812d53612 (patch) | |
| tree | e304ac9a1043c8903a402067e2cc381f7fd6f15c /llvm/test/CodeGen/X86 | |
| parent | f47d6b38c7a61d50db4566b02719de05492dcef1 (diff) | |
| download | bcm5719-llvm-0bed9e0453e1298f4323a3ec5d94a6e812d53612.tar.gz bcm5719-llvm-0bed9e0453e1298f4323a3ec5d94a6e812d53612.zip | |
[DAGCombine] Avoid CombineZExtLogicopShiftLoad if there is free ZEXT
This patch fixes pr39098.
For the attached test case, CombineZExtLogicopShiftLoad can optimize it to
t25: i64 = Constant<1099511627775>
t35: i64 = Constant<0>
t0: ch = EntryToken
t57: i64,ch = load<(load 4 from `i40* undef`, align 8), zext from i32> t0, undef:i64, undef:i64
t58: i64 = srl t57, Constant:i8<1>
t60: i64 = and t58, Constant:i64<524287>
t29: ch = store<(store 5 into `i40* undef`, align 8), trunc to i40> t57:1, t60, undef:i64, undef:i64
But later visitANDLike transforms it to
t25: i64 = Constant<1099511627775>
t35: i64 = Constant<0>
t0: ch = EntryToken
t57: i64,ch = load<(load 4 from `i40* undef`, align 8), zext from i32> t0, undef:i64, undef:i64
t61: i32 = truncate t57
t63: i32 = srl t61, Constant:i8<1>
t64: i32 = and t63, Constant:i32<524287>
t65: i64 = zero_extend t64
t58: i64 = srl t57, Constant:i8<1>
t60: i64 = and t58, Constant:i64<524287>
t29: ch = store<(store 5 into `i40* undef`, align 8), trunc to i40> t57:1, t60, undef:i64, undef:i64
And it triggers CombineZExtLogicopShiftLoad again, causes a dead loop.
Both forms should generate same instructions, CombineZExtLogicopShiftLoad generated IR looks cleaner. But it looks more difficult to prevent visitANDLike to do the transform, so I prevent CombineZExtLogicopShiftLoad to do the transform if the ZExt is free.
Differential Revision: https://reviews.llvm.org/D57491
llvm-svn: 352792
Diffstat (limited to 'llvm/test/CodeGen/X86')
| -rw-r--r-- | llvm/test/CodeGen/X86/pr39098.ll | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/llvm/test/CodeGen/X86/pr39098.ll b/llvm/test/CodeGen/X86/pr39098.ll new file mode 100644 index 00000000000..fd586d7bb69 --- /dev/null +++ b/llvm/test/CodeGen/X86/pr39098.ll @@ -0,0 +1,20 @@ +; RUN: llc < %s -mtriple=x86_64-unknown-unknown | FileCheck %s + +define dso_local void @test_cancel2(i40* %p1, i40* %p2) { +; CHECK: # %entry +; CHECK-NEXT: movl (%rdi), %eax +; CHECK-NEXT: shrl %eax +; CHECK-NEXT: andl $524287, %eax +; CHECK-NEXT: movl %eax, (%rsi) +; CHECK-NEXT: movb $0, 4(%rsi) +; CHECK-NEXT: retq +entry: + %0 = load i40, i40* %p1, align 8 + %shl414 = shl i40 %0, 19 + %unsclear415 = and i40 %shl414, 549755813887 + %shr416 = lshr i40 %unsclear415, 20 + %unsclear417 = and i40 %shr416, 549755813887 + store i40 %unsclear417, i40* %p2, align 8 + ret void +} + |
