[llvm] [InstCombine] Allow Ephemerals when trying to remove assume. (PR #128296)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Andreas Jonson (andjo403)

<details>
<summary>Changes</summary>

Makes it possible to remove loads of nonnull pointers when the only use is an assume.

---
Full diff: https://github.com/llvm/llvm-project/pull/128296.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp (+2-1) 
- (modified) llvm/test/Transforms/InstCombine/assume.ll (+5-14) 


``````````diff
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 54f777ab20a7a..405b0c2d8d972 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3217,7 +3217,8 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
                                         m_Zero())) &&
         LHS->getOpcode() == Instruction::Load &&
         LHS->getType()->isPointerTy() &&
-        isValidAssumeForContext(II, LHS, &DT)) {
+        isValidAssumeForContext(II, LHS, &DT,
+                                /*AllowEphemerals=*/true)) {
       MDNode *MD = MDNode::get(II->getContext(), {});
       LHS->setMetadata(LLVMContext::MD_nonnull, MD);
       LHS->setMetadata(LLVMContext::MD_noundef, MD);
diff --git a/llvm/test/Transforms/InstCombine/assume.ll b/llvm/test/Transforms/InstCombine/assume.ll
index 90fa9e680bb1e..5bd8fbc823756 100644
--- a/llvm/test/Transforms/InstCombine/assume.ll
+++ b/llvm/test/Transforms/InstCombine/assume.ll
@@ -502,10 +502,9 @@ define i1 @nonnull3B(ptr %a, i1 %control) {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    br i1 [[CONTROL:%.*]], label [[TAKEN:%.*]], label [[NOT_TAKEN:%.*]]
 ; CHECK:       taken:
-; CHECK-NEXT:    [[LOAD:%.*]] = load ptr, ptr [[A:%.*]], align 8
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne ptr [[LOAD]], null
-; CHECK-NEXT:    call void @llvm.assume(i1 [[CMP]]) [ "nonnull"(ptr [[LOAD]]) ]
-; CHECK-NEXT:    ret i1 [[CMP]]
+; CHECK-NEXT:    [[LOAD:%.*]] = load ptr, ptr [[A:%.*]], align 8, !nonnull [[META6]], !noundef [[META6]]
+; CHECK-NEXT:    call void @llvm.assume(i1 true) [ "nonnull"(ptr [[LOAD]]) ]
+; CHECK-NEXT:    ret i1 true
 ; CHECK:       not_taken:
 ; CHECK-NEXT:    ret i1 false
 ;
@@ -582,16 +581,8 @@ not_taken:
 }
 
 define void @nonnull_only_ephemeral_use(ptr %p) {
-; DEFAULT-LABEL: @nonnull_only_ephemeral_use(
-; DEFAULT-NEXT:    [[A:%.*]] = load ptr, ptr [[P:%.*]], align 8
-; DEFAULT-NEXT:    [[CMP:%.*]] = icmp ne ptr [[A]], null
-; DEFAULT-NEXT:    tail call void @llvm.assume(i1 [[CMP]])
-; DEFAULT-NEXT:    ret void
-;
-; BUNDLES-LABEL: @nonnull_only_ephemeral_use(
-; BUNDLES-NEXT:    [[A:%.*]] = load ptr, ptr [[P:%.*]], align 8
-; BUNDLES-NEXT:    call void @llvm.assume(i1 true) [ "nonnull"(ptr [[A]]) ]
-; BUNDLES-NEXT:    ret void
+; CHECK-LABEL: @nonnull_only_ephemeral_use(
+; CHECK-NEXT:    ret void
 ;
   %a = load ptr, ptr %p
   %cmp = icmp ne ptr %a, null

``````````

</details>


https://github.com/llvm/llvm-project/pull/128296