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author | Yingwei Zheng <dtcxzyw2333@gmail.com> | 2024-04-29 15:51:49 +0800 |
---|---|---|
committer | Tom Stellard <tstellar@redhat.com> | 2024-04-30 11:06:37 -0700 |
commit | 6350acdb134d2e494c029ef2f83ccbc1a1462ba3 (patch) | |
tree | e69e1ae101490ba6db0ecebc0280b221d5a68f9f | |
parent | f341c76b946142366d2b4eabcb1190347be4665b (diff) | |
download | llvm-6350acdb134d2e494c029ef2f83ccbc1a1462ba3.zip llvm-6350acdb134d2e494c029ef2f83ccbc1a1462ba3.tar.gz llvm-6350acdb134d2e494c029ef2f83ccbc1a1462ba3.tar.bz2 |
[CGP] Drop poison-generating flags after hoisting (#90382)
See the following case:
```
define i8 @src1(i8 %x) {
entry:
%cmp = icmp eq i8 %x, -1
br i1 %cmp, label %exit, label %if.then
if.then:
%inc = add nuw nsw i8 %x, 1
br label %exit
exit:
%retval = phi i8 [ %inc, %if.then ], [ -1, %entry ]
ret i8 %retval
}
define i8 @tgt1(i8 %x) {
entry:
%inc = add nuw nsw i8 %x, 1
%0 = icmp eq i8 %inc, 0
br i1 %0, label %exit, label %if.then
if.then: ; preds = %entry
br label %exit
exit: ; preds = %if.then, %entry
%retval = phi i8 [ %inc, %if.then ], [ -1, %entry ]
ret i8 %retval
}
```
`optimizeBranch` converts `icmp eq X, -1` into cmp to zero on RISC-V and
hoists the add into the entry block. Poison-generating flags should be
dropped as they don't still hold.
Proof: https://alive2.llvm.org/ce/z/sP7mvK
Fixes https://github.com/llvm/llvm-project/issues/90380
(cherry picked from commit ab12bba0aad800c1805eca2ea937da958c1854c8)
-rw-r--r-- | llvm/lib/CodeGen/CodeGenPrepare.cpp | 2 | ||||
-rw-r--r-- | llvm/test/Transforms/CodeGenPrepare/ARM/branch-on-zero.ll | 23 | ||||
-rw-r--r-- | llvm/test/Transforms/CodeGenPrepare/RISCV/convert-to-eqz.ll | 80 |
3 files changed, 105 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp index 8ee1f19..1cca56f 100644 --- a/llvm/lib/CodeGen/CodeGenPrepare.cpp +++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp @@ -8154,6 +8154,7 @@ static bool optimizeBranch(BranchInst *Branch, const TargetLowering &TLI, IRBuilder<> Builder(Branch); if (UI->getParent() != Branch->getParent()) UI->moveBefore(Branch); + UI->dropPoisonGeneratingFlags(); Value *NewCmp = Builder.CreateCmp(ICmpInst::ICMP_EQ, UI, ConstantInt::get(UI->getType(), 0)); LLVM_DEBUG(dbgs() << "Converting " << *Cmp << "\n"); @@ -8167,6 +8168,7 @@ static bool optimizeBranch(BranchInst *Branch, const TargetLowering &TLI, IRBuilder<> Builder(Branch); if (UI->getParent() != Branch->getParent()) UI->moveBefore(Branch); + UI->dropPoisonGeneratingFlags(); Value *NewCmp = Builder.CreateCmp(Cmp->getPredicate(), UI, ConstantInt::get(UI->getType(), 0)); LLVM_DEBUG(dbgs() << "Converting " << *Cmp << "\n"); diff --git a/llvm/test/Transforms/CodeGenPrepare/ARM/branch-on-zero.ll b/llvm/test/Transforms/CodeGenPrepare/ARM/branch-on-zero.ll index ff5cef7..25dfb3c 100644 --- a/llvm/test/Transforms/CodeGenPrepare/ARM/branch-on-zero.ll +++ b/llvm/test/Transforms/CodeGenPrepare/ARM/branch-on-zero.ll @@ -211,6 +211,29 @@ else: ret i32 %l } +define i32 @sub10_else_drop_nuw(i32 %a) { +; CHECK-LABEL: @sub10_else_drop_nuw( +; CHECK-NEXT: entry: +; CHECK-NEXT: [[L:%.*]] = sub i32 [[A:%.*]], 10 +; CHECK-NEXT: [[TMP0:%.*]] = icmp eq i32 [[L]], 0 +; CHECK-NEXT: br i1 [[TMP0]], label [[THEN:%.*]], label [[ELSE:%.*]] +; CHECK: then: +; CHECK-NEXT: ret i32 0 +; CHECK: else: +; CHECK-NEXT: ret i32 [[L]] +; +entry: + %c = icmp eq i32 %a, 10 + br i1 %c, label %then, label %else + +then: + ret i32 0 + +else: + %l = sub nuw i32 %a, 10 + ret i32 %l +} + define i32 @subm10_then(i32 %a) { ; CHECK-LABEL: @subm10_then( ; CHECK-NEXT: entry: diff --git a/llvm/test/Transforms/CodeGenPrepare/RISCV/convert-to-eqz.ll b/llvm/test/Transforms/CodeGenPrepare/RISCV/convert-to-eqz.ll new file mode 100644 index 0000000..a6909d1 --- /dev/null +++ b/llvm/test/Transforms/CodeGenPrepare/RISCV/convert-to-eqz.ll @@ -0,0 +1,80 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4 +; RUN: opt -codegenprepare -S -mtriple=riscv64 < %s | FileCheck %s + +define i8 @hoist_add(i8 %x) { +; CHECK-LABEL: define i8 @hoist_add( +; CHECK-SAME: i8 [[X:%.*]]) { +; CHECK-NEXT: entry: +; CHECK-NEXT: [[INC:%.*]] = add i8 [[X]], 1 +; CHECK-NEXT: [[TMP0:%.*]] = icmp eq i8 [[INC]], 0 +; CHECK-NEXT: br i1 [[TMP0]], label [[EXIT:%.*]], label [[IF_THEN:%.*]] +; CHECK: if.then: +; CHECK-NEXT: br label [[EXIT]] +; CHECK: exit: +; CHECK-NEXT: [[RETVAL:%.*]] = phi i8 [ [[INC]], [[IF_THEN]] ], [ -1, [[ENTRY:%.*]] ] +; CHECK-NEXT: ret i8 [[RETVAL]] +; +entry: + %cmp = icmp eq i8 %x, -1 + br i1 %cmp, label %exit, label %if.then + +if.then: + %inc = add nuw nsw i8 %x, 1 + br label %exit + +exit: + %retval = phi i8 [ %inc, %if.then ], [ -1, %entry ] + ret i8 %retval +} + +define i8 @hoist_lshr(i8 %x) { +; CHECK-LABEL: define i8 @hoist_lshr( +; CHECK-SAME: i8 [[X:%.*]]) { +; CHECK-NEXT: entry: +; CHECK-NEXT: [[INC:%.*]] = lshr i8 [[X]], 3 +; CHECK-NEXT: [[TMP0:%.*]] = icmp eq i8 [[INC]], 0 +; CHECK-NEXT: br i1 [[TMP0]], label [[EXIT:%.*]], label [[IF_THEN:%.*]] +; CHECK: if.then: +; CHECK-NEXT: br label [[EXIT]] +; CHECK: exit: +; CHECK-NEXT: [[RETVAL:%.*]] = phi i8 [ [[INC]], [[IF_THEN]] ], [ -1, [[ENTRY:%.*]] ] +; CHECK-NEXT: ret i8 [[RETVAL]] +; +entry: + %cmp = icmp ult i8 %x, 8 + br i1 %cmp, label %exit, label %if.then + +if.then: + %inc = lshr exact i8 %x, 3 + br label %exit + +exit: + %retval = phi i8 [ %inc, %if.then ], [ -1, %entry ] + ret i8 %retval +} + +define i8 @nomove_add(i8 %x) { +; CHECK-LABEL: define i8 @nomove_add( +; CHECK-SAME: i8 [[X:%.*]]) { +; CHECK-NEXT: entry: +; CHECK-NEXT: [[INC:%.*]] = add i8 [[X]], 1 +; CHECK-NEXT: [[TMP0:%.*]] = icmp eq i8 [[INC]], 0 +; CHECK-NEXT: br i1 [[TMP0]], label [[EXIT:%.*]], label [[IF_THEN:%.*]] +; CHECK: if.then: +; CHECK-NEXT: br label [[EXIT]] +; CHECK: exit: +; CHECK-NEXT: [[RETVAL:%.*]] = phi i8 [ [[INC]], [[IF_THEN]] ], [ -1, [[ENTRY:%.*]] ] +; CHECK-NEXT: ret i8 [[RETVAL]] +; +entry: + %inc = add nuw nsw i8 %x, 1 + %cmp = icmp eq i8 %x, -1 + br i1 %cmp, label %exit, label %if.then + +if.then: + br label %exit + +exit: + %retval = phi i8 [ %inc, %if.then ], [ -1, %entry ] + ret i8 %retval +} |