[llvm] fe00ab4 - [NFC][MIR] Fix extra whitespace in MIR printing (#162928)

[via llvm-commits]

Author: Rahul Joshi
Date: 2025-10-13T13:05:05-07:00
New Revision: fe00ab4c108d46b8ed092862f67534828f20300d

URL: https://github.com/llvm/llvm-project/commit/fe00ab4c108d46b8ed092862f67534828f20300d
DIFF: https://github.com/llvm/llvm-project/commit/fe00ab4c108d46b8ed092862f67534828f20300d.diff

LOG: [NFC][MIR] Fix extra whitespace in MIR printing (#162928)

Fix a whitespace regression in MIR printing that was introduced in
https://github.com/llvm/llvm-project/pull/137361.

The default value for `ListSeparator` is `", "`, so we don't need to
print an additional space in front of tokens for optional symbols and
other things printed after operands.

Note, the modified LIT test will fail at trunk without the fix,
demonstrating that the extra space before `, pre-instr-symbol <mcsymbol
>` on Line 63 exists currently and is fixed with this change.

Added: 
    

Modified: 
    llvm/include/llvm/ADT/StringExtras.h
    llvm/lib/CodeGen/MIRPrinter.cpp
    llvm/test/CodeGen/MIR/AArch64/return-address-signing.mir
    llvm/unittests/ADT/StringExtrasTest.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/ADT/StringExtras.h b/llvm/include/llvm/ADT/StringExtras.h
index 7d81c63485be2..2440e7678a831 100644
--- a/llvm/include/llvm/ADT/StringExtras.h
+++ b/llvm/include/llvm/ADT/StringExtras.h
@@ -529,13 +529,15 @@ inline std::string join_items(Sep Separator, Args &&... Items) {
 class ListSeparator {
   bool First = true;
   StringRef Separator;
+  StringRef Prefix;
 
 public:
-  ListSeparator(StringRef Separator = ", ") : Separator(Separator) {}
+  ListSeparator(StringRef Separator = ", ", StringRef Prefix = "")
+      : Separator(Separator), Prefix(Prefix) {}
   operator StringRef() {
     if (First) {
       First = false;
-      return {};
+      return Prefix;
     }
     return Separator;
   }

diff  --git a/llvm/lib/CodeGen/MIRPrinter.cpp b/llvm/lib/CodeGen/MIRPrinter.cpp
index 96428cd7ea84e..1d54d72336860 100644
--- a/llvm/lib/CodeGen/MIRPrinter.cpp
+++ b/llvm/lib/CodeGen/MIRPrinter.cpp
@@ -862,48 +862,46 @@ static void printMI(raw_ostream &OS, MFPrintState &State,
 
   OS << TII->getName(MI.getOpcode());
 
-  LS = ListSeparator();
+  // Print a space after the opcode if any additional tokens are printed.
+  LS = ListSeparator(", ", " ");
 
-  if (I < E) {
-    OS << ' ';
-    for (; I < E; ++I) {
-      OS << LS;
-      printMIOperand(OS, State, MI, I, TRI, TII, ShouldPrintRegisterTies,
-                     PrintedTypes, MRI, /*PrintDef=*/true);
-    }
+  for (; I < E; ++I) {
+    OS << LS;
+    printMIOperand(OS, State, MI, I, TRI, TII, ShouldPrintRegisterTies,
+                   PrintedTypes, MRI, /*PrintDef=*/true);
   }
 
   // Print any optional symbols attached to this instruction as-if they were
   // operands.
   if (MCSymbol *PreInstrSymbol = MI.getPreInstrSymbol()) {
-    OS << LS << " pre-instr-symbol ";
+    OS << LS << "pre-instr-symbol ";
     MachineOperand::printSymbol(OS, *PreInstrSymbol);
   }
   if (MCSymbol *PostInstrSymbol = MI.getPostInstrSymbol()) {
-    OS << LS << " post-instr-symbol ";
+    OS << LS << "post-instr-symbol ";
     MachineOperand::printSymbol(OS, *PostInstrSymbol);
   }
   if (MDNode *HeapAllocMarker = MI.getHeapAllocMarker()) {
-    OS << LS << " heap-alloc-marker ";
+    OS << LS << "heap-alloc-marker ";
     HeapAllocMarker->printAsOperand(OS, State.MST);
   }
   if (MDNode *PCSections = MI.getPCSections()) {
-    OS << LS << " pcsections ";
+    OS << LS << "pcsections ";
     PCSections->printAsOperand(OS, State.MST);
   }
   if (MDNode *MMRA = MI.getMMRAMetadata()) {
-    OS << LS << " mmra ";
+    OS << LS << "mmra ";
     MMRA->printAsOperand(OS, State.MST);
   }
   if (uint32_t CFIType = MI.getCFIType())
-    OS << LS << " cfi-type " << CFIType;
+    OS << LS << "cfi-type " << CFIType;
 
   if (auto Num = MI.peekDebugInstrNum())
-    OS << LS << " debug-instr-number " << Num;
+    OS << LS << "debug-instr-number " << Num;
 
   if (PrintLocations) {
     if (const DebugLoc &DL = MI.getDebugLoc()) {
-      OS << LS << " debug-location ";
+      OS << LS << "debug-location ";
       DL->printAsOperand(OS, State.MST);
     }
   }

diff  --git a/llvm/test/CodeGen/MIR/AArch64/return-address-signing.mir b/llvm/test/CodeGen/MIR/AArch64/return-address-signing.mir
index 1030917c87419..302f70fc15192 100644
--- a/llvm/test/CodeGen/MIR/AArch64/return-address-signing.mir
+++ b/llvm/test/CodeGen/MIR/AArch64/return-address-signing.mir
@@ -1,4 +1,4 @@
-# RUN: llc -mtriple=aarch64 -run-pass=prologepilog -run-pass=aarch64-ptrauth -o - %s 2>&1 | FileCheck %s
+# RUN: llc -mtriple=aarch64 -run-pass=prologepilog -run-pass=aarch64-ptrauth -o - %s 2>&1 | FileCheck --strict-whitespace %s
 --- |
   target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
   target triple = "aarch64"

diff  --git a/llvm/unittests/ADT/StringExtrasTest.cpp b/llvm/unittests/ADT/StringExtrasTest.cpp
index fbaed38da5943..af88f88949b77 100644
--- a/llvm/unittests/ADT/StringExtrasTest.cpp
+++ b/llvm/unittests/ADT/StringExtrasTest.cpp
@@ -290,6 +290,12 @@ TEST(StringExtrasTest, ListSeparator) {
   EXPECT_EQ(S, "");
   S = LS2;
   EXPECT_EQ(S, " ");
+
+  ListSeparator LS3(",", "{");
+  S = LS3;
+  EXPECT_EQ(S, "{");
+  S = LS3;
+  EXPECT_EQ(S, ",");
 }
 
 TEST(StringExtrasTest, toStringAPInt) {