[llvm] fcd32d6 - [AMDGPU] Fix function pointer argument bug in AMDGPU Propagate Attributes pass.

[Sebastian Neubauer via llvm-commits]

Author: jweightma
Date: 2021-05-26T16:40:15+02:00
New Revision: fcd32d62c0675abccac7b7f919bb0df52b6c4262

URL: https://github.com/llvm/llvm-project/commit/fcd32d62c0675abccac7b7f919bb0df52b6c4262
DIFF: https://github.com/llvm/llvm-project/commit/fcd32d62c0675abccac7b7f919bb0df52b6c4262.diff

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

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.

Reviewed By: arsenm, madhur13490

Differential Revision: https://reviews.llvm.org/D101847

Added: 
    llvm/test/CodeGen/AMDGPU/propagate-attributes-function-pointer-argument.ll

Modified: 
    llvm/lib/Target/AMDGPU/AMDGPUPropagateAttributes.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/AMDGPU/AMDGPUPropagateAttributes.cpp b/llvm/lib/Target/AMDGPU/AMDGPUPropagateAttributes.cpp
index cd71c7a16c73b..0e4c26170a8fa 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUPropagateAttributes.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUPropagateAttributes.cpp
@@ -249,7 +249,11 @@ bool AMDGPUPropagateAttributes::process() {
         if (!I)
           continue;
         CallBase *CI = dyn_cast<CallBase>(I);
-        if (!CI)
+        // Only propagate attributes if F is the called function. Specifically,
+        // do not propagate attributes if F is passed as an argument.
+        // FIXME: handle bitcasted callee, e.g.
+        // %retval = call i8* bitcast (i32* ()* @f to i8* ()*)()
+        if (!CI || CI->getCalledOperand() != &F)
           continue;
         Function *Caller = CI->getCaller();
         if (!Caller || !Visited.insert(CI).second)

diff  --git a/llvm/test/CodeGen/AMDGPU/propagate-attributes-function-pointer-argument.ll b/llvm/test/CodeGen/AMDGPU/propagate-attributes-function-pointer-argument.ll
new file mode 100644
index 0000000000000..370c5cc17e91f
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/propagate-attributes-function-pointer-argument.ll
@@ -0,0 +1,40 @@
+; 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-LABEL: define amdgpu_kernel void @thiswasabug() #0
+; CHECK-NOT: call void @g(void ()* @g.1)
+; CHECK-DAG: call void @f(void ()* @g.1)
+; CHECK-DAG: call void @g()
+define amdgpu_kernel void @thiswasabug() #0 {
+    ; no replacement, but @g should be renamed to @g.1
+    call void @f(void ()* @g)
+
+    ; this should call the clone, which takes the name @g
+    call 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.
+; CHECK-DAG: define private void @g.1() #1
+; CHECK-DAG: define internal void @g() #2
+define private void @g() #1 {
+    ret void
+}
+
+attributes #0 = { noinline }
+attributes #1 = { noinline "amdgpu-waves-per-eu"="1,10" }