[PATCH] D101847: [AMDGPU] Fix function pointer argument bug in AMDGPU Propagate Attributes pass.

[Jacob Weightman via Phabricator via llvm-commits]

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This patch fixes a bug in the AMDGPU Propagate Attributes pass where a call
instruction with a function pointer argument is identified as a user of the
passed function, and illegally replaces the called function of the
instruction with the function argument.

For example, given functions f and g with appropriate types, the following
illegal transformation could occur without this fix:
call void @f(void ()* @g)
-->
call void @g(void ()* @g.1)

The solution introduced in this patch is to prevent the cloning and
substitution if the instruction's called function and the function which
might be cloned do not match.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D101847

Files:
  llvm/lib/Target/AMDGPU/AMDGPUPropagateAttributes.cpp
  llvm/test/CodeGen/AMDGPU/propagate-attributes-function-pointer-argument.ll


Index: llvm/test/CodeGen/AMDGPU/propagate-attributes-function-pointer-argument.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AMDGPU/propagate-attributes-function-pointer-argument.ll
@@ -0,0 +1,32 @@
+; This is a regression test for a bug in the AMDGPU Propagate Attributes pass
+; where a call instruction's callee could be replaced with a function pointer
+; passed to the original call instruction as an argument.
+;
+; Example:
+; `call void @f(void ()* @g)`
+; could become
+; `call void @g(void ()* @g.1)`
+; which is invalid IR.
+
+; RUN: opt -S -mtriple=amdgcn-amd-amdhsa -amdgpu-propagate-attributes-late %s | FileCheck %s
+
+; CHECK: define amdgpu_kernel void @thiswasabug() #0
+; CHECK: call void @f(void ()* @g)
+define amdgpu_kernel void @thiswasabug() #0 {
+    call void @f(void ()* @g)
+    ret void
+}
+
+define private void @f(void ()* nocapture %0) #0 {
+    ret void
+}
+
+; In order to expose this bug, it is necessary that `g` have one of the
+; propagated attributes, so that a clone and substitution would take place if g
+; were actually the function being called.
+define private void @g() #1 {
+    ret void
+}
+
+attributes #0 = { noinline }
+attributes #1 = { noinline "amdgpu-waves-per-eu"="1,10" }
Index: llvm/lib/Target/AMDGPU/AMDGPUPropagateAttributes.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/AMDGPUPropagateAttributes.cpp
+++ llvm/lib/Target/AMDGPU/AMDGPUPropagateAttributes.cpp
@@ -249,7 +249,7 @@
         if (!I)
           continue;
         CallBase *CI = dyn_cast<CallBase>(I);
-        if (!CI)
+        if (!CI || CI->getCalledFunction() != &F)
           continue;
         Function *Caller = CI->getCaller();
         if (!Caller || !Visited.insert(CI).second)


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