Fix FastISel bug in boolean returns for PowerPC.

For PPC targets, FastISel does not take the sign extension information into account when selecting return instructions whose operands are constants. A consequence of this is that the return of boolean values is not correct. This patch fixes the problem by evaluating the sign extension information also for constants, forwarding this information to PPCMaterializeInt which takes this information to drive the sign extension during the materialization. 

llvm-svn: 217993

1 files changed, 18 insertions, 7 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCFastISel.cpp b/llvm/lib/Target/PowerPC/PPCFastISel.cpp
index 91646ad5a5f..99aa4eaf643 100644
--- a/llvm/lib/Target/PowerPC/PPCFastISel.cpp
+++ b/llvm/lib/Target/PowerPC/PPCFastISel.cpp
@@ -152,7 +152,7 @@ class PPCFastISel final : public FastISel {
                            unsigned DestReg, bool IsZExt);
     unsigned PPCMaterializeFP(const ConstantFP *CFP, MVT VT);
     unsigned PPCMaterializeGV(const GlobalValue *GV, MVT VT);
-    unsigned PPCMaterializeInt(const Constant *C, MVT VT);
+    unsigned PPCMaterializeInt(const Constant *C, MVT VT, bool UseSExt = true);
     unsigned PPCMaterialize32BitInt(int64_t Imm,
                                     const TargetRegisterClass *RC);
     unsigned PPCMaterialize64BitInt(int64_t Imm,
@@ -1547,13 +1547,23 @@ bool PPCFastISel::SelectRet(const Instruction *I) {
 
     // Special case for returning a constant integer of any size.
     // Materialize the constant as an i64 and copy it to the return
-    // register. This avoids an unnecessary extend or truncate.
+    // register. We still need to worry about properly extending the sign. E.g:
+    // If the constant has only one bit, it means it is a boolean. Therefore
+    // we can't use PPCMaterializeInt because it extends the sign which will
+    // cause negations of the returned value to be incorrect as they are
+    // implemented as the flip of the least significant bit.
     if (isa<ConstantInt>(*RV)) {
       const Constant *C = cast<Constant>(RV);
-      unsigned SrcReg = PPCMaterializeInt(C, MVT::i64);
-      unsigned RetReg = ValLocs[0].getLocReg();
+
+      CCValAssign &VA = ValLocs[0];
+
+      unsigned RetReg = VA.getLocReg();
+      unsigned SrcReg = PPCMaterializeInt(C, MVT::i64,
+                                          VA.getLocInfo() == CCValAssign::SExt);
+
       BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
-              TII.get(TargetOpcode::COPY), RetReg).addReg(SrcReg);
+            TII.get(TargetOpcode::COPY), RetReg).addReg(SrcReg);
+
       RetRegs.push_back(RetReg);
 
     } else {
@@ -2013,7 +2023,8 @@ unsigned PPCFastISel::PPCMaterialize64BitInt(int64_t Imm,
 
 // Materialize an integer constant into a register, and return
 // the register number (or zero if we failed to handle it).
-unsigned PPCFastISel::PPCMaterializeInt(const Constant *C, MVT VT) {
+unsigned PPCFastISel::PPCMaterializeInt(const Constant *C, MVT VT,
+                                                           bool UseSExt) {
   // If we're using CR bit registers for i1 values, handle that as a special
   // case first.
   if (VT == MVT::i1 && PPCSubTarget->useCRBits()) {
@@ -2037,7 +2048,7 @@ unsigned PPCFastISel::PPCMaterializeInt(const Constant *C, MVT VT) {
     unsigned Opc = (VT == MVT::i64) ? PPC::LI8 : PPC::LI;
     unsigned ImmReg = createResultReg(RC);
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(Opc), ImmReg)
-      .addImm(CI->getSExtValue());
+      .addImm( (UseSExt) ? CI->getSExtValue() : CI->getZExtValue() );
     return ImmReg;
   }