r196370 - [SystemZ] Fix handling of pass-by-pointer arguments

[Richard Sandiford]

Author: rsandifo
Date: Wed Dec  4 03:59:57 2013
New Revision: 196370

URL: http://llvm.org/viewvc/llvm-project?rev=196370&view=rev
Log:
[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.

Modified:
    cfe/trunk/lib/CodeGen/TargetInfo.cpp
    cfe/trunk/test/CodeGen/systemz-inline-asm.c

Modified: cfe/trunk/lib/CodeGen/TargetInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/TargetInfo.cpp?rev=196370&r1=196369&r2=196370&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/TargetInfo.cpp (original)
+++ cfe/trunk/lib/CodeGen/TargetInfo.cpp Wed Dec  4 03:59:57 2013
@@ -4573,7 +4573,7 @@ ABIArgInfo SystemZABIInfo::classifyArgum
   // 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::classifyArgum
     // 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::classifyArgum
 
   // Non-structure compounds are passed indirectly.
   if (isCompoundType(Ty))
-    return ABIArgInfo::getIndirect(0);
+    return ABIArgInfo::getIndirect(0, /*ByVal=*/false);
 
   return ABIArgInfo::getDirect(0);
 }

Modified: cfe/trunk/test/CodeGen/systemz-inline-asm.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/systemz-inline-asm.c?rev=196370&r1=196369&r2=196370&view=diff
==============================================================================
--- cfe/trunk/test/CodeGen/systemz-inline-asm.c (original)
+++ cfe/trunk/test/CodeGen/systemz-inline-asm.c Wed Dec  4 03:59:57 2013
@@ -123,7 +123,7 @@ double test_f64(double f, double g) {
 long double test_f128(long double f, long double g) {
   asm("axbr %0, %2" : "=f" (f) : "0" (f), "f" (g));
   return f;
-// CHECK: define void @test_f128(fp128* noalias nocapture sret [[DEST:%.*]], fp128* byval nocapture readonly, fp128* byval nocapture readonly)
+// CHECK: define void @test_f128(fp128* noalias nocapture sret [[DEST:%.*]], fp128* nocapture readonly, fp128* nocapture readonly)
 // CHECK: %f = load fp128* %0
 // CHECK: %g = load fp128* %1
 // CHECK: [[RESULT:%.*]] = tail call fp128 asm "axbr $0, $2", "=f,0,f"(fp128 %f, fp128 %g)