release/18.x: [Codegen][X86] Fix /HOTPATCH with clang-cl and inline asm (#87639) #88388
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
@aganea What do you think about merging this PR to the release branch? |
|
@llvm/pr-subscribers-backend-x86 Author: None (llvmbot) ChangesBackport ec1af63 Requested by: @aganea Full diff: https://github.com/llvm/llvm-project/pull/88388.diff 2 Files Affected:
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 58ebe023cd61ec..7ce0aa22b99795 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -959,8 +959,10 @@ void X86AsmPrinter::LowerPATCHABLE_OP(const MachineInstr &MI,
SmallString<256> Code;
unsigned MinSize = MI.getOperand(0).getImm();
- if (NextMI != MI.getParent()->end()) {
+ if (NextMI != MI.getParent()->end() && !NextMI->isInlineAsm()) {
// Lower the next MachineInstr to find its byte size.
+ // If the next instruction is inline assembly, we skip lowering it for now,
+ // and assume we should always generate NOPs.
MCInst MCI;
MCIL.Lower(&*NextMI, MCI);
diff --git a/llvm/test/CodeGen/X86/patchable-prologue.ll b/llvm/test/CodeGen/X86/patchable-prologue.ll
index 71a392845fdea3..43761e3d1e1eb9 100644
--- a/llvm/test/CodeGen/X86/patchable-prologue.ll
+++ b/llvm/test/CodeGen/X86/patchable-prologue.ll
@@ -193,3 +193,20 @@ do.body: ; preds = %do.body, %entry
do.end: ; preds = %do.body
ret void
}
+
+
+; Test that inline asm is properly hotpatched. We currently don't examine the
+; asm instruction when printing it, thus we always emit patching NOPs.
+
+; 64: inline_asm:
+; 64-NEXT: # %bb.0:
+; 64-NEXT: xchgw %ax, %ax # encoding: [0x66,0x90]
+; 64-NEXT: #APP
+; 64-NEXT: int3 # encoding: [0xcc]
+; 64-NEXT: #NO_APP
+
+define dso_local void @inline_asm() "patchable-function"="prologue-short-redirect" {
+entry:
+ call void asm sideeffect "int3", "~{dirflag},~{fpsr},~{flags}"()
+ ret void
+}
|
aganea
approved these changes
Apr 11, 2024
There was a problem hiding this comment.
It think this should be good to go, but ideally I'd like someone else to sign off please. @phoebewang @KanRobert @sylvain-audi
I think it's safe and good to go too. |
This fixes an edge case where functions starting with inline assembly would assert while trying to lower that inline asm instruction. After this PR, for now we always add a no-op (xchgw in this case) without considering the size of the next inline asm instruction. We might want to revisit this in the future. This fixes Unreal Engine 5.3.2 compilation with clang-cl and /HOTPATCH. Should close llvm#56234 (cherry picked from commit ec1af63)
|
Hi @aganea (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Backport ec1af63
Requested by: @aganea