[GlobalISel][Legalizer] Widening the second src op of shifts bug fix
The second source operand of G_SHL, G_ASHR, and G_LSHR must preserve its
value as a (small) unsigned integer, therefore its incorrect to widen it
in any way but by zero extending it.
G_SHL was using G_ANYEXT and G_ASHR - G_SEXT (which is correct for their
destination and first source operands, but not the "number of bits to
shift" operand).
Generally, shifts aren't as similar to regular binary operations as it
might seem, for instance, they aren't commutative nor associative and
the second source operand usually requires a special treatment.
Reviewers: bogner, javed.absar, aivchenk, rovka
Reviewed By: bogner
Subscribers: igorb, kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D46413
llvm-svn: 331926
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index e1b9c6b..410c3b7 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -621,7 +621,6 @@
case TargetOpcode::G_OR:
case TargetOpcode::G_XOR:
case TargetOpcode::G_SUB:
- case TargetOpcode::G_SHL:
// Perform operation at larger width (any extension is fine here, high bits
// don't affect the result) and then truncate the result back to the
// original type.
@@ -631,15 +630,32 @@
MIRBuilder.recordInsertion(&MI);
return Legalized;
+ case TargetOpcode::G_SHL:
+ widenScalarSrc(MI, WideTy, 1, TargetOpcode::G_ANYEXT);
+ // The "number of bits to shift" operand must preserve its value as an
+ // unsigned integer:
+ widenScalarSrc(MI, WideTy, 2, TargetOpcode::G_ZEXT);
+ widenScalarDst(MI, WideTy);
+ MIRBuilder.recordInsertion(&MI);
+ return Legalized;
+
case TargetOpcode::G_SDIV:
case TargetOpcode::G_SREM:
- case TargetOpcode::G_ASHR:
widenScalarSrc(MI, WideTy, 1, TargetOpcode::G_SEXT);
widenScalarSrc(MI, WideTy, 2, TargetOpcode::G_SEXT);
widenScalarDst(MI, WideTy);
MIRBuilder.recordInsertion(&MI);
return Legalized;
+ case TargetOpcode::G_ASHR:
+ widenScalarSrc(MI, WideTy, 1, TargetOpcode::G_SEXT);
+ // The "number of bits to shift" operand must preserve its value as an
+ // unsigned integer:
+ widenScalarSrc(MI, WideTy, 2, TargetOpcode::G_ZEXT);
+ widenScalarDst(MI, WideTy);
+ MIRBuilder.recordInsertion(&MI);
+ return Legalized;
+
case TargetOpcode::G_UDIV:
case TargetOpcode::G_UREM:
case TargetOpcode::G_LSHR:
