[llvm] [AsmParser] Correctly handle .ifeqs nested in other conditional directives (PR #132713)

[Oliver Stannard via llvm-commits]

https://github.com/ostannard updated https://github.com/llvm/llvm-project/pull/132713

>From a52ebfa57fc4a245a1d5ed85203862a93c9378a5 Mon Sep 17 00:00:00 2001
From: Oliver Stannard <oliver.stannard at arm.com>
Date: Mon, 24 Mar 2025 10:49:22 +0000
Subject: [PATCH 1/2] [AsmParser] Correctly handle .ifeqs nested in other
 conditional directives

The parser function used for the .ifeqs and .ifnes directives was
missing the check for whether we are currently in an ignored block of an
outer conditional directive, causing the block to be evaluated when it
should not, for example:

.if 0
  .ifeqs "a", "a"
    // Should not be evaluated, but is
    nop
  .endif
.endif
---
 llvm/lib/MC/MCParser/AsmParser.cpp | 55 ++++++++++++++++--------------
 llvm/test/MC/AsmParser/ifeqs.s     | 11 ++++++
 llvm/test/MC/AsmParser/ifnes.s     | 10 ++++++
 3 files changed, 51 insertions(+), 25 deletions(-)

diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index c11c01e52fc2e..b0f0c5e5db2ce 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -5224,37 +5224,42 @@ bool AsmParser::parseDirectiveIfc(SMLoc DirectiveLoc, bool ExpectEqual) {
 /// parseDirectiveIfeqs
 ///   ::= .ifeqs string1, string2
 bool AsmParser::parseDirectiveIfeqs(SMLoc DirectiveLoc, bool ExpectEqual) {
-  if (Lexer.isNot(AsmToken::String)) {
-    if (ExpectEqual)
-      return TokError("expected string parameter for '.ifeqs' directive");
-    return TokError("expected string parameter for '.ifnes' directive");
-  }
+  TheCondStack.push_back(TheCondState);
+  TheCondState.TheCond = AsmCond::IfCond;
 
-  StringRef String1 = getTok().getStringContents();
-  Lex();
+  if (TheCondState.Ignore) {
+    eatToEndOfStatement();
+  } else {
+    if (Lexer.isNot(AsmToken::String)) {
+      if (ExpectEqual)
+        return TokError("expected string parameter for '.ifeqs' directive");
+      return TokError("expected string parameter for '.ifnes' directive");
+    }
 
-  if (Lexer.isNot(AsmToken::Comma)) {
-    if (ExpectEqual)
-      return TokError(
-          "expected comma after first string for '.ifeqs' directive");
-    return TokError("expected comma after first string for '.ifnes' directive");
-  }
+    StringRef String1 = getTok().getStringContents();
+    Lex();
 
-  Lex();
+    if (Lexer.isNot(AsmToken::Comma)) {
+      if (ExpectEqual)
+        return TokError(
+            "expected comma after first string for '.ifeqs' directive");
+      return TokError("expected comma after first string for '.ifnes' directive");
+    }
 
-  if (Lexer.isNot(AsmToken::String)) {
-    if (ExpectEqual)
-      return TokError("expected string parameter for '.ifeqs' directive");
-    return TokError("expected string parameter for '.ifnes' directive");
-  }
+    Lex();
 
-  StringRef String2 = getTok().getStringContents();
-  Lex();
+    if (Lexer.isNot(AsmToken::String)) {
+      if (ExpectEqual)
+        return TokError("expected string parameter for '.ifeqs' directive");
+      return TokError("expected string parameter for '.ifnes' directive");
+    }
 
-  TheCondStack.push_back(TheCondState);
-  TheCondState.TheCond = AsmCond::IfCond;
-  TheCondState.CondMet = ExpectEqual == (String1 == String2);
-  TheCondState.Ignore = !TheCondState.CondMet;
+    StringRef String2 = getTok().getStringContents();
+    Lex();
+
+    TheCondState.CondMet = ExpectEqual == (String1 == String2);
+    TheCondState.Ignore = !TheCondState.CondMet;
+  }
 
   return false;
 }
diff --git a/llvm/test/MC/AsmParser/ifeqs.s b/llvm/test/MC/AsmParser/ifeqs.s
index 05a26a237fcd3..fd5f1a84980a2 100644
--- a/llvm/test/MC/AsmParser/ifeqs.s
+++ b/llvm/test/MC/AsmParser/ifeqs.s
@@ -18,3 +18,14 @@
 // CHECK-NOT: .byte 0
 // CHECK: .byte 1
 
+
+.if 0
+  .ifeqs "alpha", "alpha"
+    .byte 2
+  .else
+    .byte 3
+  .endif
+.endif
+
+// CHECK-NOT: .byte 2
+// CHECK-NOT: .byte 3
diff --git a/llvm/test/MC/AsmParser/ifnes.s b/llvm/test/MC/AsmParser/ifnes.s
index 7a3cbe0264e1b..bd7dc3b637b21 100644
--- a/llvm/test/MC/AsmParser/ifnes.s
+++ b/llvm/test/MC/AsmParser/ifnes.s
@@ -20,3 +20,13 @@
 # CHECK: .byte 1
 .ifnes "equal", "equal" ; .byte 0 ; .else ; .byte 1 ; .endif
 
+.if 0
+  .ifnes "alpha", "alpha"
+    .byte 2
+  .else
+    .byte 3
+  .endif
+.endif
+
+// CHECK-NOT: .byte 2
+// CHECK-NOT: .byte 3

>From 882b1232b7a307adec428785e565d5f61ca595cb Mon Sep 17 00:00:00 2001
From: Oliver Stannard <oliver.stannard at arm.com>
Date: Mon, 24 Mar 2025 11:05:50 +0000
Subject: [PATCH 2/2] clang-format

---
 llvm/lib/MC/MCParser/AsmParser.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index b0f0c5e5db2ce..9448e7b301e28 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -5243,7 +5243,8 @@ bool AsmParser::parseDirectiveIfeqs(SMLoc DirectiveLoc, bool ExpectEqual) {
       if (ExpectEqual)
         return TokError(
             "expected comma after first string for '.ifeqs' directive");
-      return TokError("expected comma after first string for '.ifnes' directive");
+      return TokError(
+          "expected comma after first string for '.ifnes' directive");
     }
 
     Lex();