[PATCH] D112626: Convert float to double on __builtin_dump_struct

Aaron Ballman via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Tue Nov 30 08:14:38 PST 2021

aaron.ballman added a reviewer: paulsemel.
aaron.ballman added a subscriber: paulsemel.
aaron.ballman added a comment.

Adding @paulsemel to the reviewer list as he was the original author of this functionality (I commit on his behalf which is how I showed up on the git blame).

Comment at: clang/lib/CodeGen/CGBuiltin.cpp:2090-2094
+    // Variadic functions expect the caller to promote float to double.
+    if (CanonicalType == Context.FloatTy) {
+      FieldPtr =
+          CGF.Builder.CreateFPExt(FieldPtr, CGF.ConvertType(Context.DoubleTy));
+    }
This change is an improvement as far as it goes, but I think we might be missing other floating-point promotions here. For example, `__fp16` fields also seem to be unusable: https://godbolt.org/z/z3a45f9YE

Also, we don't seem to handle the integer promotions at all (but still get correct results there), so I think we're getting the correct behavior there by chance rather than by design. Oh, yeah, note the differences here: https://godbolt.org/z/f13eq3668

  %7 = load i8, i8* %4, align 1, !dbg !217
  %8 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([6 x i8], [6 x i8]* @2, i32 0, i32 0), i8 %7), !dbg !217

  %2 = load i8, i8* %1, align 1, !dbg !222
  %3 = zext i8 %2 to i32, !dbg !222
  %4 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), i32 %3), !dbg !223
I think we should probably fix all of the promotion problems at once rather than piecemeal.

  rG LLVM Github Monorepo



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