[PATCH] D65542: [PeepholeOptimizer] Don't assume bitcast def always has input

[Quentin Colombet via Phabricator via llvm-commits]

qcolombet added inline comments.


================
Comment at: llvm/test/CodeGen/PowerPC/bitcast-peephole.mir:2
+# RUN: llc -mtriple=powerpc64le-linux-gnu -run-pass=peephole-opt -verify-machineinstrs -o - %s | FileCheck %s
+# REQUIRES: asserts
+
----------------
jsji wrote:
> qcolombet wrote:
> > qcolombet wrote:
> > > Instead of requiring assertion, I would just explicitly check that the number of operands is correct.
> > > You can use `update_mir_test_check.py` to generate the check lines for this.
> > Scratch my last comment on the number of operands!
> > Still would generating the CHECK lines with the update script would have caught the bug without having to rely on asserts?
> I gave it a try. Unfotunately, no, we can't caught this without assert.
> 
> ```
> [~/build-nonassert] $ cat ../llvm-project/llvm/test/CodeGen/PowerPC/bitcast-peephole.mir
> # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
> # RUN: llc -mtriple=powerpc64le-linux-gnu -run-pass=peephole-opt -verify-machineinstrs -o - %s | FileCheck %s
> 
> ---
> name:            bitCast
> tracksRegLiveness: true
> body:             |
>   bb.0.entry:
>     ; CHECK-LABEL: name: bitCast
>     ; CHECK: [[XXLEQVOnes:%[0-9]+]]:vsrc = XXLEQVOnes
>     ; CHECK: $v2 = COPY [[XXLEQVOnes]]
>     ; CHECK: BLR8 implicit $lr8, implicit $rm, implicit $v2
>     %0:vsrc = XXLEQVOnes
>     $v2 = COPY %0
>     BLR8 implicit $lr8, implicit $rm, implicit $v2
> 
> ...
> 
> # This used to hit an assertion:
> #   llvm/include/llvm/CodeGen/MachineInstr.h:417: const
> #   llvm::MachineOperand &llvm::MachineInstr::getOperand(unsigned int)
> #   const: Assertion `i < getNumOperands() && "getOperand() out of range!"' failed.
> #
> [~/build-nonassert] $ bin/llvm-lit ../llvm-project/llvm/test/CodeGen/PowerPC/bitcast-peephole.mir -v
> -- Testing: 1 tests, single process --
> PASS: LLVM :: CodeGen/PowerPC/bitcast-peephole.mir (1 of 1)
> Testing Time: 0.04s
>   Expected Passes    : 1
> 
> [~/build] $ bin/llvm-lit ../llvm-project/llvm/test/CodeGen/PowerPC/bitcast-peephole.mir 
> -- Testing: 1 tests, single process --
> FAIL: LLVM :: CodeGen/PowerPC/bitcast-peephole.mir (1 of 1)
> Testing Time: 0.32s
> ********************
> Failing Tests (1):
>     LLVM :: CodeGen/PowerPC/bitcast-peephole.mir
> 
>   Unexpected Failures: 1
> 
> ```
> I gave it a try. Unfotunately, no, we can't caught this without assert.

So we end up generating correct code by luck for this case?


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  https://reviews.llvm.org/D65542/new/

https://reviews.llvm.org/D65542