[llvm-commits] [llvm] r53767 - in /llvm/trunk: lib/Target/CBackend/CBackend.cpp test/CodeGen/CBackend/2007-02-23-NameConflicts.ll test/CodeGen/CBackend/pr2408.ll

[Dan Gohman]

Author: djg
Date: Fri Jul 18 13:43:12 2008
New Revision: 53767

URL: http://llvm.org/viewvc/llvm-project?rev=53767&view=rev
Log:
In the CBackend, use casts to force integer add, subtract, and
multiply to be done as unsigned, so that they have well defined
behavior on overflow. This fixes PR2408.

Added:
    llvm/trunk/test/CodeGen/CBackend/pr2408.ll
Modified:
    llvm/trunk/lib/Target/CBackend/CBackend.cpp
    llvm/trunk/test/CodeGen/CBackend/2007-02-23-NameConflicts.ll

Modified: llvm/trunk/lib/Target/CBackend/CBackend.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/CBackend/CBackend.cpp?rev=53767&r1=53766&r2=53767&view=diff

==============================================================================
--- llvm/trunk/lib/Target/CBackend/CBackend.cpp (original)
+++ llvm/trunk/lib/Target/CBackend/CBackend.cpp Fri Jul 18 13:43:12 2008
@@ -1116,6 +1116,13 @@
   const Type *Ty = CE->getOperand(0)->getType();
   bool TypeIsSigned = false;
   switch (CE->getOpcode()) {
+  case Instruction::Add:
+  case Instruction::Sub:
+  case Instruction::Mul:
+    // We need to cast integer arithmetic so that it is always performed
+    // as unsigned, to avoid undefined behavior on overflow.
+    if (!Ty->isIntOrIntVector()) break;
+    // FALL THROUGH
   case Instruction::LShr:
   case Instruction::URem: 
   case Instruction::UDiv: NeedsExplicitCast = true; break;
@@ -1174,6 +1181,13 @@
     default:
       // for most instructions, it doesn't matter
       break; 
+    case Instruction::Add:
+    case Instruction::Sub:
+    case Instruction::Mul:
+      // We need to cast integer arithmetic so that it is always performed
+      // as unsigned, to avoid undefined behavior on overflow.
+      if (!OpTy->isIntOrIntVector()) break;
+      // FALL THROUGH
     case Instruction::LShr:
     case Instruction::UDiv:
     case Instruction::URem:
@@ -1294,6 +1308,13 @@
 bool CWriter::writeInstructionCast(const Instruction &I) {
   const Type *Ty = I.getOperand(0)->getType();
   switch (I.getOpcode()) {
+  case Instruction::Add:
+  case Instruction::Sub:
+  case Instruction::Mul:
+    // We need to cast integer arithmetic so that it is always performed
+    // as unsigned, to avoid undefined behavior on overflow.
+    if (!Ty->isIntOrIntVector()) break;
+    // FALL THROUGH
   case Instruction::LShr:
   case Instruction::URem: 
   case Instruction::UDiv: 
@@ -1334,6 +1355,13 @@
     default:
       // for most instructions, it doesn't matter
       break; 
+    case Instruction::Add:
+    case Instruction::Sub:
+    case Instruction::Mul:
+      // We need to cast integer arithmetic so that it is always performed
+      // as unsigned, to avoid undefined behavior on overflow.
+      if (!OpTy->isIntOrIntVector()) break;
+      // FALL THROUGH
     case Instruction::LShr:
     case Instruction::UDiv:
     case Instruction::URem: // Cast to unsigned first

Modified: llvm/trunk/test/CodeGen/CBackend/2007-02-23-NameConflicts.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/CBackend/2007-02-23-NameConflicts.ll?rev=53767&r1=53766&r2=53767&view=diff

==============================================================================
--- llvm/trunk/test/CodeGen/CBackend/2007-02-23-NameConflicts.ll (original)
+++ llvm/trunk/test/CodeGen/CBackend/2007-02-23-NameConflicts.ll Fri Jul 18 13:43:12 2008
@@ -1,7 +1,8 @@
 ; PR1164
 ; RUN: llvm-as < %s | llc -march=c | grep {llvm_cbe_A = \\*llvm_cbe_G;}
 ; RUN: llvm-as < %s | llc -march=c | grep {llvm_cbe_B = \\*(&ltmp_0_1);}
-; RUN: llvm-as < %s | llc -march=c | grep {return (llvm_cbe_A + llvm_cbe_B);}
+; RUN: llvm-as < %s | llc -march=c | grep {return (((unsigned int )(((unsigned int )llvm_cbe_A) + ((unsigned int )llvm_cbe_B))));}
+
 @G = global i32 123
 @ltmp_0_1 = global i32 123
 

Added: llvm/trunk/test/CodeGen/CBackend/pr2408.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/CBackend/pr2408.ll?rev=53767&view=auto

==============================================================================
--- llvm/trunk/test/CodeGen/CBackend/pr2408.ll (added)
+++ llvm/trunk/test/CodeGen/CBackend/pr2408.ll Fri Jul 18 13:43:12 2008
@@ -0,0 +1,12 @@
+; RUN: llvm-as < %s | llc -march=c | grep {\\* ((unsigned int )}
+; PR2408
+
+define i32 @a(i32 %a) {
+entry:
+        %shr = ashr i32 %a, 0           ; <i32> [#uses=1]
+        %shr2 = ashr i32 2, 0           ; <i32> [#uses=1]
+        %mul = mul i32 %shr, %shr2              ; <i32> [#uses=1]
+        %shr4 = ashr i32 2, 0           ; <i32> [#uses=1]
+        %div = sdiv i32 %mul, %shr4             ; <i32> [#uses=1]
+        ret i32 %div
+}