Subzero: Be more strict about i1 calculations.

src/IceTargetLoweringX8632.cpp

Index: src/IceTargetLoweringX8632.cpp
diff --git a/src/IceTargetLoweringX8632.cpp b/src/IceTargetLoweringX8632.cpp
index 7b977585b5c6e910cb6bc8f2e02f4b678c518d15..6237b8a1718647da420649630047caa64cd48698 100644
--- a/src/IceTargetLoweringX8632.cpp
+++ b/src/IceTargetLoweringX8632.cpp
@@ -1965,8 +1965,13 @@ void TargetX8632::lowerCast(const InstCast *Inst) {
       // dst = t1
       size_t DestBits = X86_CHAR_BIT * typeWidthInBytes(Dest->getType());
       Constant *ShiftAmount = Ctx->getConstantInt(IceType_i32, DestBits - 1);
-      Variable *T = NULL;
-      _mov(T, Src0RM);
+      Variable *T = makeReg(Dest->getType());
+      if (typeWidthInBytes(Dest->getType()) <=
+          typeWidthInBytes(Src0RM->getType())) {
+        _mov(T, Src0RM);
+      } else {
+        _movzx(T, Src0RM);

[jvoung (off chromium), 2014/09/06 17:53:02]

Not sure I understand why it's movzx (for a sign-ext cast)? I guess it doesn't
matter because the shift will only take the bottom bit anyway?

[Jim Stichnoth, 2014/09/06 21:57:27]

Clarified in a comment.  Movsx/movzx are only needed for widening, and you're
right that the following shl/sar will overwrite the bits.

I chose movzx due to the not necessarily founded suspicion that movzx may be
micro-architecturally faster than movsx.

+      }
       _shl(T, ShiftAmount);
       _sar(T, ShiftAmount);
       _mov(Dest, T);
@@ -2038,6 +2043,8 @@ void TargetX8632::lowerCast(const InstCast *Inst) {
       // t1 = trunc Src0RM; Dest = t1
       Variable *T = NULL;
       _mov(T, Src0RM);
+      if (Dest->getType() == IceType_i1)
+        _and(T, Ctx->getConstantInt(IceType_i1, 1));
       _mov(Dest, T);
     }
     break;
@@ -2081,6 +2088,8 @@ void TargetX8632::lowerCast(const InstCast *Inst) {
       Variable *T_2 = makeReg(Dest->getType());
       _cvt(T_1, Src0RM);
       _mov(T_2, T_1); // T_1 and T_2 may have different integer types
+      if (Dest->getType() == IceType_i1)
+        _and(T_2, Ctx->getConstantInt(IceType_i1, 1));
       _mov(Dest, T_2);
       T_2->setPreferredRegister(T_1, true);
     }
@@ -2116,6 +2125,8 @@ void TargetX8632::lowerCast(const InstCast *Inst) {
       Variable *T_2 = makeReg(Dest->getType());
       _cvt(T_1, Src0RM);
       _mov(T_2, T_1); // T_1 and T_2 may have different integer types
+      if (Dest->getType() == IceType_i1)
+        _and(T_2, Ctx->getConstantInt(IceType_i1, 1));
       _mov(Dest, T_2);
       T_2->setPreferredRegister(T_1, true);
     }