[PATCH] D130126: fix bug for useless malloc elimination in CodeGenPrepare

[Ruobing Han via Phabricator via llvm-commits]

drcut created this revision.
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Put AllocationFn check before I->willReturn can allow CodeGenPrepare to remove useless malloc instruction


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D130126

Files:
  llvm/lib/Transforms/Utils/Local.cpp
  llvm/test/CodeGen/Generic/dead-allocation.ll


Index: llvm/test/CodeGen/Generic/dead-allocation.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/Generic/dead-allocation.ll
@@ -0,0 +1,19 @@
+; Eliminate the dead allocation instruction
+; RUN: opt -mtriple arm64-apple-darwin -codegenprepare < %s -S | FileCheck %s
+
+ at .str = private unnamed_addr constant [2 x i8] c"a\00", align 1
+
+define void @func() {
+; CHECK-LABEL: @func
+; CHECK-LABEL: entry:
+; CHECK-NEXT:  ret void
+entry:
+  %0 = tail call noalias noundef nonnull dereferenceable(32) ptr @_Znwm(i64 noundef 32)
+  %1 = icmp ugt ptr %0, @.str
+  tail call void @llvm.assume(i1 %1)
+  ret void
+}
+
+declare noundef nonnull ptr @_Znwm(i64 noundef) local_unnamed_addr
+
+declare void @llvm.assume(i1 noundef)
\ No newline at end of file
Index: llvm/lib/Transforms/Utils/Local.cpp
===================================================================
--- llvm/lib/Transforms/Utils/Local.cpp
+++ llvm/lib/Transforms/Utils/Local.cpp
@@ -439,6 +439,9 @@
     return true;
   }
 
+  if (isAllocationFn(I, TLI) && isAllocRemovable(cast<CallBase>(I), TLI))
+    return true;
+
   if (!I->willReturn())
     return false;
 
@@ -489,9 +492,6 @@
     }
   }
 
-  if (isAllocationFn(I, TLI) && isAllocRemovable(cast<CallBase>(I), TLI))
-    return true;
-
   if (CallInst *CI = isFreeCall(I, TLI))
     if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0)))
       return C->isNullValue() || isa<UndefValue>(C);


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