[WebAssembly] Don't stackify multi-def instructions (#200429) - #3
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This commit updates the `WebAssemblyRegStackify.cpp` pass to specifically exclude attempting to stackify the first def of a multi-def instruction. As the previous comments indicate this is possible to do in some situations, but the current logic is incomplete and has led to miscompilations such as llvm#98323 and llvm#199910. One option would be to make the logic more robust, but in lieu of that in the meantime the change here is to completely disable stackification in these situations. This provides at least a "known working" base to build on later and fixes the known regressions around this. Closes llvm#98323 Closes llvm#199910 Backport to LLVM 21.1.2. Adapt the multivalue.ll REGS check to the older WebAssembly register-printer syntax. (cherry picked from commit b472674)
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This commit updates the
WebAssemblyRegStackify.cpppass to specifically exclude attempting to stackify the first def of a multi-def instruction. As the previous comments indicate this is possible to do in some situations, but the current logic is incomplete and has led to miscompilations such as llvm#98323 and llvm#199910. One option would be to make the logic more robust, but in lieu of that in the meantime the change here is to completely disable stackification in these situations. This provides at least a "known working" base to build on later and fixes the known regressions around this.Closes llvm#98323
Closes llvm#199910
Backport to LLVM 21.1.2. Adapt the multivalue.ll REGS check to the older WebAssembly register-printer syntax.
(cherry picked from commit b472674)