JIT: Skip GC info for trivial async calls for x86 #121941
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For x86 we only report GC pointers live in callee save registers, and we also avoid reporting any trivial call. There is compensating code upstream of the GC reporting that returns for trivial calls, but this code did not account for the GC ref returned for async continuations. Thus it was possible that we made it into the GC encoder with a trivial call and then hit an assert.
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Pull request overview
This PR fixes an assertion failure in the GC encoder for x86 when processing trivial async calls. The issue occurred because the code that masks out return registers for GC reporting only accounted for the standard integer return register (EAX), but not the long return register pair (EDX:EAX) or the async continuation return register (ECX). The fix extends the mask to include all three register sets.
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AndyAyersMS
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Nov 25, 2025
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Nov 25, 2025
The fix presumably merged in #121941.
MichalStrehovsky
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Nov 26, 2025
The fix presumably merged in #121941. Cc @dotnet/ilc-contrib
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For x86 we only report GC pointers live in callee save registers, and we also avoid reporting any trivial call.
There is compensating code upstream of the GC reporting that returns for trivial calls, but this code did not account for the GC ref returned for async continuations. Thus it was possible that we made it into the GC encoder with a trivial call and then hit an assert.
Fix #121872