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author | Nikita Popov <npopov@redhat.com> | 2023-09-29 14:00:23 +0200 |
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committer | Nikita Popov <npopov@redhat.com> | 2023-10-02 12:40:20 +0200 |
commit | 3b25407d977d9ed3dbcaccd4f8850b65e95d70fd (patch) | |
tree | 8b4d04fb81e7d290608310d28e7dc1791c113a01 /llvm/lib/IR/Constants.cpp | |
parent | 2214026e957397cc6385f778b28d570485a31856 (diff) | |
download | llvm-3b25407d977d9ed3dbcaccd4f8850b65e95d70fd.zip llvm-3b25407d977d9ed3dbcaccd4f8850b65e95d70fd.tar.gz llvm-3b25407d977d9ed3dbcaccd4f8850b65e95d70fd.tar.bz2 |
[IR] Mark zext/sext constant expressions as undesirable
Introduce isDesirableCastOp() which determines whether IR builder
and constant folding should produce constant expressions for a
given cast type. This mirrors what we do for binary operators.
Mark zext/sext as undesirable, which prevents most creations of such
constant expressions. This is still somewhat incomplete and there
are a few more places that can create zext/sext expressions.
This is part of the work for
https://discourse.llvm.org/t/rfc-remove-most-constant-expressions/63179.
The reason for the odd result in the constantexpr-fneg.c test is
that initially the "a[]" global is created with an [0 x i32] type,
at which point the icmp expression cannot be folded. Later it is
replaced with an [1 x i32] global and the icmp gets folded away.
But at that point we no longer fold the zext.
Diffstat (limited to 'llvm/lib/IR/Constants.cpp')
-rw-r--r-- | llvm/lib/IR/Constants.cpp | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp index 6589bd3..ba18da9 100644 --- a/llvm/lib/IR/Constants.cpp +++ b/llvm/lib/IR/Constants.cpp @@ -2331,6 +2331,28 @@ bool ConstantExpr::isSupportedBinOp(unsigned Opcode) { } } +bool ConstantExpr::isDesirableCastOp(unsigned Opcode) { + switch (Opcode) { + case Instruction::ZExt: + case Instruction::SExt: + return false; + case Instruction::Trunc: + case Instruction::FPTrunc: + case Instruction::FPExt: + case Instruction::UIToFP: + case Instruction::SIToFP: + case Instruction::FPToUI: + case Instruction::FPToSI: + case Instruction::PtrToInt: + case Instruction::IntToPtr: + case Instruction::BitCast: + case Instruction::AddrSpaceCast: + return true; + default: + llvm_unreachable("Argument must be cast opcode"); + } +} + Constant *ConstantExpr::getSizeOf(Type* Ty) { // sizeof is implemented as: (i64) gep (Ty*)null, 1 // Note that a non-inbounds gep is used, as null isn't within any object. |