In asm's, output operands with matching input constraints

have to be registers, per gcc documentation.  This affects
the logic for determining what "g" should lower to.  PR 7393.
A couple of existing testcases are affected.

llvm-svn: 107079

lib/CodeGen/SelectionDAG/TargetLowering.cpp

@@ -2547,12 +2547,12 @@ static void ChooseConstraint(TargetLowering::AsmOperandInfo &OpInfo,
   unsigned BestIdx = 0;
   TargetLowering::ConstraintType BestType = TargetLowering::C_Unknown;
   int BestGenerality = -1;
-  
+
   // Loop over the options, keeping track of the most general one.
   for (unsigned i = 0, e = OpInfo.Codes.size(); i != e; ++i) {
     TargetLowering::ConstraintType CType =
       TLI.getConstraintType(OpInfo.Codes[i]);
-    
+
     // If this is an 'other' constraint, see if the operand is valid for it.
     // For example, on X86 we might have an 'rI' constraint.  If the operand
     // is an integer in the range [0..31] we want to use I (saving a load
@@ -2570,6 +2570,11 @@ static void ChooseConstraint(TargetLowering::AsmOperandInfo &OpInfo,
       }
     }
     
+    // Things with matching constraints can only be registers, per gcc
+    // documentation.  This mainly affects "g" constraints.
+    if (CType == TargetLowering::C_Memory && OpInfo.hasMatchingInput())
+      continue;
+    
     // This constraint letter is more general than the previous one, use it.
     int Generality = getConstraintGenerality(CType);
     if (Generality > BestGenerality) {

test/CodeGen/X86/2008-09-18-inline-asm-2.ll

@@ -1,5 +1,5 @@
-; RUN: llc < %s -march=x86 | grep "#%ebp %esi %edi 8(%edx) %eax (%ebx)"
-; RUN: llc < %s -march=x86 -regalloc=fast  | grep "#%edi %ebx %edx 8(%ebp) %eax (%esi)"
+; RUN: llc < %s -march=x86 | grep "#%ebp %edi %ebx 8(%esi) %eax %dl"
+; RUN: llc < %s -march=x86 -regalloc=fast  | grep "#%ebx %esi %edi 8(%ebp) %eax %dl"
 
 ; The 1st, 2nd, 3rd and 5th registers above must all be different.  The registers
 ; referenced in the 4th and 6th operands must not be the same as the 1st or 5th

test/CodeGen/X86/2010-06-28-matched-g-constraint.ll

@@ -0,0 +1,11 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin11 | FileCheck %s
+; Any register is OK for %0, but it must be a register, not memory.
+
+define i32 @foo() nounwind ssp {
+entry:
+; CHECK: GCROOT %eax
+  %_r = alloca i32, align 4                       ; <i32*> [#uses=2]
+  call void asm "/* GCROOT $0 */", "=*imr,0,~{dirflag},~{fpsr},~{flags}"(i32* %_r, i32 4) nounwind
+  %0 = load i32* %_r, align 4                     ; <i32> [#uses=1]
+  ret i32 %0
+}

test/FrontendC/2010-06-17-asmcrash.c

@@ -12,5 +12,5 @@ void avg_pixels8_mmx2(uint8_t *block, const uint8_t *pixels, int line_size, int
      :"+g"(h), "+S"(pixels), "+D"(block)
      :"r" ((x86_reg)line_size)         
      :"%""rax", "memory");
-// CHECK: # (%rsp) %rsi %rdi %rcx
+// CHECK: # %ecx %rsi %rdi %rdx
  }