When CodeGen'ing unoptimized code, there may be unfolded constant expressions

in global initializers. Instead of aborting, attempt to fold them on the
spot. If folding succeeds, emit the folded expression instead.

This fixes PR6255.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95583 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -25,6 +25,7 @@
 #include "llvm/CodeGen/MachineJumpTableInfo.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/Analysis/ConstantFolding.h"
 #include "llvm/Analysis/DebugInfo.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
@@ -887,15 +888,16 @@ static const MCExpr *LowerConstant(const Constant *CV, AsmPrinter &AP) {
   }
   
   switch (CE->getOpcode()) {
-  case Instruction::ZExt:
-  case Instruction::SExt:
-  case Instruction::FPTrunc:
-  case Instruction::FPExt:
-  case Instruction::UIToFP:
-  case Instruction::SIToFP:
-  case Instruction::FPToUI:
-  case Instruction::FPToSI:
-  default: llvm_unreachable("FIXME: Don't support this constant cast expr");
+  default:
+    // If the code isn't optimized, there may be outstanding folding
+    // opportunities. Attempt to fold the expression using TargetData as a
+    // last resort before giving up.
+    if (Constant *C = ConstantFoldConstantExpression(CE, AP.TM.getTargetData()))
+      return LowerConstant(C, AP);
+#ifndef NDEBUG
+    CE->dump();
+#endif
+    llvm_unreachable("FIXME: Don't support this constant expr");
   case Instruction::GetElementPtr: {
     const TargetData &TD = *AP.TM.getTargetData();
     // Generate a symbolic expression for the byte address

test/CodeGen/X86/ptrtoint-constexpr.ll

@@ -6,3 +6,9 @@
 ; CHECK: .quad	r&4294967295
 
 @r = global %union.x { i64 ptrtoint (%union.x* @r to i64) }, align 4
+
+; CHECK:	.globl x
+; CHECK: x:
+; CHECK: .quad	3
+
+@x = global i64 mul (i64 3, i64 ptrtoint (i2* getelementptr (i2* null, i64 1) to i64))