[LangRef] inline asm: the instructions are treated opaquely #157080
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@llvm/pr-subscribers-llvm-ir Author: Ralf Jung (RalfJung) ChangesThis wasn't true until recently, but #156571 got fixed to make it true. I was not entirely sure where to put this; for now I made it a new paragraph fairly early on in the inline asm docs. Cc @nikic @jyknight @efriedma-quic Full diff: https://github.com/llvm/llvm-project/pull/157080.diff 1 Files Affected:
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index e64b9343b7622..bdf90c8465d74 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -5229,6 +5229,11 @@ flag that indicates whether or not the inline asm expression has side effects,
and a flag indicating whether the function containing the asm needs to align its
stack conservatively.
+LLVM will treat the actual instructions entirely opaquely (i.e. no optimizations
+will be performed based on the contents of the template string). Only the
+operand constraints are used to deduce what the expression may do during
+execution.
+
The template string supports argument substitution of the operands using "``$``"
followed by a number, to indicate substitution of the given register/memory
location, as specified by the constraint string. "``${NUM:MODIFIER}``" may also
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This wasn't true until recently, but #156571 got fixed to make it true.
I was not entirely sure where to put this; for now I made it a new paragraph fairly early on in the inline asm docs.
Cc @nikic @jyknight @efriedma-quic