[SystemZ] Fix handling of pass-by-pointer arguments

I'd misunderstood getIndirect() to mean that the argument should be passed
as a pointer at the ABI level, with the ByVal argument choosing caller-copy
semantics over no-caller-copy (callee-copy-on-write) semantics.  But
getIndirect(x) actually means that x is passed by pointer at the IR
level but (at least on all other targets I looked at) directly at the
ABI level.  getIndirect(x, false) selects a pointer to a caller-made
copy, which is what SystemZ was aiming for.

This fixes a miscompilation of c-index-test.  Structure arguments were being
passed by pointer, but no copy was being made, so a write in the callee
stomped over a caller's local variable.

llvm-svn: 196370

1 files changed, 3 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 3d0c9f16016..76acf871da2 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -4573,7 +4573,7 @@ ABIArgInfo SystemZABIInfo::classifyArgumentType(QualType Ty) const {
   // Values that are not 1, 2, 4 or 8 bytes in size are passed indirectly.
   uint64_t Size = getContext().getTypeSize(Ty);
   if (Size != 8 && Size != 16 && Size != 32 && Size != 64)
-    return ABIArgInfo::getIndirect(0);
+    return ABIArgInfo::getIndirect(0, /*ByVal=*/false);
 
   // Handle small structures.
   if (const RecordType *RT = Ty->getAs<RecordType>()) {
@@ -4581,7 +4581,7 @@ ABIArgInfo SystemZABIInfo::classifyArgumentType(QualType Ty) const {
     // fail the size test above.
     const RecordDecl *RD = RT->getDecl();
     if (RD->hasFlexibleArrayMember())
-      return ABIArgInfo::getIndirect(0);
+      return ABIArgInfo::getIndirect(0, /*ByVal=*/false);
 
     // The structure is passed as an unextended integer, a float, or a double.
     llvm::Type *PassTy;
@@ -4598,7 +4598,7 @@ ABIArgInfo SystemZABIInfo::classifyArgumentType(QualType Ty) const {
 
   // Non-structure compounds are passed indirectly.
   if (isCompoundType(Ty))
-    return ABIArgInfo::getIndirect(0);
+    return ABIArgInfo::getIndirect(0, /*ByVal=*/false);
 
   return ABIArgInfo::getDirect(0);
 }