commit d7b650cc721f7dbb52cbfa0a50797e61990d7990
author Sam Parker <sam.parker@arm.com> Thu May 09 11:56:16 2019 +0000
committer Sam Parker <sam.parker@arm.com> Thu May 09 11:56:16 2019 +0000
tree 720a9289b3b505e542787857e9387986898efe5b
parent 933e305ed909fd93f9c2d7107b28e4ec2fea38ab

[ARM][CGP] Guard against signext args and sitofp

Add an Argument that has the SExtAttr attached, as well as SIToFP
instructions, as values that generate sign bits. SIToFP doesn't
strictly do this and could be treated as a sink to be sign-extended.

Differential Revision: https://reviews.llvm.org/D61381

llvm-svn: 360331

llvm/lib/Target/ARM/ARMCodeGenPrepare.cpp

diff --git a/llvm/lib/Target/ARM/ARMCodeGenPrepare.cpp b/llvm/lib/Target/ARM/ARMCodeGenPrepare.cpp
index b59f05d..93a715a 100644
--- a/llvm/lib/Target/ARM/ARMCodeGenPrepare.cpp
+++ b/llvm/lib/Target/ARM/ARMCodeGenPrepare.cpp
@@ -175,13 +175,17 @@
 
 }
 
-static bool generateSignBits(Value *V) {
+static bool GenerateSignBits(Value *V) {
+  if (auto *Arg = dyn_cast<Argument>(V))
+    return Arg->hasSExtAttr();
+
   if (!isa<Instruction>(V))
     return false;
 
   unsigned Opc = cast<Instruction>(V)->getOpcode();
   return Opc == Instruction::AShr || Opc == Instruction::SDiv ||
-         Opc == Instruction::SRem;
+         Opc == Instruction::SRem || Opc == Instruction::SExt ||
+         Opc == Instruction::SIToFP;
 }
 
 static bool EqualTypeSize(Value *V) {
@@ -414,7 +418,7 @@
   if (!isa<Instruction>(V))
     return true;
 
-  if (generateSignBits(V))
+  if (GenerateSignBits(V))
     return false;
 
   return !isa<OverflowingBinaryOperator>(V);
@@ -833,6 +837,11 @@
     return EqualTypeSize(I->getOperand(0));
   }
 
+  if (GenerateSignBits(V)) {
+    LLVM_DEBUG(dbgs() << "ARM CGP: No, instruction can generate sign bits.\n");
+    return false;
+  }
+
   // Memory instructions
   if (isa<StoreInst>(V) || isa<GetElementPtrInst>(V))
     return true;
@@ -849,9 +858,6 @@
       isa<LoadInst>(V))
     return isSupportedType(V);
 
-  if (isa<SExtInst>(V))
-    return false;
-
   if (auto *Cast = dyn_cast<CastInst>(V))
     return isSupportedType(Cast) || isSupportedType(Cast->getOperand(0));
 
@@ -868,10 +874,6 @@
   if (!isSupportedType(V))
     return false;
 
-  if (generateSignBits(V)) {
-    LLVM_DEBUG(dbgs() << "ARM CGP: No, instruction can generate sign bits.\n");
-    return false;
-  }
   return true;
 }