[llvm] Optimize loops in MC. (PR #98114)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-mc

Author: Dmitriy Chestnykh (chestnykh)

<details>
<summary>Changes</summary>

https://llvm.org/docs/CodingStandards.html tells us that we should avoid evaluating `.end()` each time if possible.

---
Full diff: https://github.com/llvm/llvm-project/pull/98114.diff


3 Files Affected:

- (modified) llvm/lib/MC/MCParser/AsmParser.cpp (+3-3) 
- (modified) llvm/lib/MC/MCParser/MasmParser.cpp (+3-3) 
- (modified) llvm/lib/MC/XCOFFObjectWriter.cpp (+14-11) 


``````````diff
diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index f3caa90eedfb1..dba56b15424d5 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -6116,8 +6116,8 @@ bool AsmParser::parseMSInlineAsm(
   const char *AsmStart = ASMString.begin();
   const char *AsmEnd = ASMString.end();
   array_pod_sort(AsmStrRewrites.begin(), AsmStrRewrites.end(), rewritesSort);
-  for (auto it = AsmStrRewrites.begin(); it != AsmStrRewrites.end(); ++it) {
-    const AsmRewrite &AR = *it;
+  for (auto I = AsmStrRewrites.begin(), E = AsmStrRewrites.end(); I != E; ++I) {
+    const AsmRewrite &AR = *I;
     // Check if this has already been covered by another rewrite...
     if (AR.Done)
       continue;
@@ -6160,7 +6160,7 @@ bool AsmParser::parseMSInlineAsm(
         SMLoc OffsetLoc = SMLoc::getFromPointer(AR.IntelExp.OffsetName.data());
         size_t OffsetLen = OffsetName.size();
         auto rewrite_it = std::find_if(
-            it, AsmStrRewrites.end(), [&](const AsmRewrite &FusingAR) {
+            I, AsmStrRewrites.end(), [&](const AsmRewrite &FusingAR) {
               return FusingAR.Loc == OffsetLoc && FusingAR.Len == OffsetLen &&
                      (FusingAR.Kind == AOK_Input ||
                       FusingAR.Kind == AOK_CallInput);
diff --git a/llvm/lib/MC/MCParser/MasmParser.cpp b/llvm/lib/MC/MCParser/MasmParser.cpp
index 653cc64b4c36a..f64b7f62d61d0 100644
--- a/llvm/lib/MC/MCParser/MasmParser.cpp
+++ b/llvm/lib/MC/MCParser/MasmParser.cpp
@@ -7474,8 +7474,8 @@ bool MasmParser::parseMSInlineAsm(
   const char *AsmStart = ASMString.begin();
   const char *AsmEnd = ASMString.end();
   array_pod_sort(AsmStrRewrites.begin(), AsmStrRewrites.end(), rewritesSort);
-  for (auto it = AsmStrRewrites.begin(); it != AsmStrRewrites.end(); ++it) {
-    const AsmRewrite &AR = *it;
+  for (auto I = AsmStrRewrites.begin(), E = AsmStrRewrites.end(); I != E; ++I) {
+    const AsmRewrite &AR = *I;
     // Check if this has already been covered by another rewrite...
     if (AR.Done)
       continue;
@@ -7518,7 +7518,7 @@ bool MasmParser::parseMSInlineAsm(
         SMLoc OffsetLoc = SMLoc::getFromPointer(AR.IntelExp.OffsetName.data());
         size_t OffsetLen = OffsetName.size();
         auto rewrite_it = std::find_if(
-            it, AsmStrRewrites.end(), [&](const AsmRewrite &FusingAR) {
+            I, AsmStrRewrites.end(), [&](const AsmRewrite &FusingAR) {
               return FusingAR.Loc == OffsetLoc && FusingAR.Len == OffsetLen &&
                      (FusingAR.Kind == AOK_Input ||
                       FusingAR.Kind == AOK_CallInput);
diff --git a/llvm/lib/MC/XCOFFObjectWriter.cpp b/llvm/lib/MC/XCOFFObjectWriter.cpp
index 03a4ee831d895..122f19367ae7b 100644
--- a/llvm/lib/MC/XCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/XCOFFObjectWriter.cpp
@@ -1385,11 +1385,12 @@ void XCOFFObjectWriter::addExceptionEntry(
 unsigned XCOFFObjectWriter::getExceptionSectionSize() {
   unsigned EntryNum = 0;
 
-  for (auto it = ExceptionSection.ExceptionTable.begin();
-       it != ExceptionSection.ExceptionTable.end(); ++it)
+  for (auto I = ExceptionSection.ExceptionTable.begin(),
+            E = ExceptionSection.ExceptionTable.end();
+      I != E; ++I)
     // The size() gets +1 to account for the initial entry containing the
     // symbol table index.
-    EntryNum += it->second.Entries.size() + 1;
+    EntryNum += I->second.Entries.size() + 1;
 
   return EntryNum * (is64Bit() ? XCOFF::ExceptionSectionEntrySize64
                                : XCOFF::ExceptionSectionEntrySize32);
@@ -1397,11 +1398,12 @@ unsigned XCOFFObjectWriter::getExceptionSectionSize() {
 
 unsigned XCOFFObjectWriter::getExceptionOffset(const MCSymbol *Symbol) {
   unsigned EntryNum = 0;
-  for (auto it = ExceptionSection.ExceptionTable.begin();
-       it != ExceptionSection.ExceptionTable.end(); ++it) {
-    if (Symbol == it->second.FunctionSymbol)
+  for (auto I = ExceptionSection.ExceptionTable.begin(),
+            E = ExceptionSection.ExceptionTable.end();
+      I != E; ++I) {
+    if (Symbol == I->second.FunctionSymbol)
       break;
-    EntryNum += it->second.Entries.size() + 1;
+    EntryNum += I->second.Entries.size() + 1;
   }
   return EntryNum * (is64Bit() ? XCOFF::ExceptionSectionEntrySize64
                                : XCOFF::ExceptionSectionEntrySize32);
@@ -1667,17 +1669,18 @@ void XCOFFObjectWriter::writeSectionForDwarfSectionEntry(
 void XCOFFObjectWriter::writeSectionForExceptionSectionEntry(
     const MCAssembler &Asm, ExceptionSectionEntry &ExceptionEntry,
     uint64_t &CurrentAddressLocation) {
-  for (auto it = ExceptionEntry.ExceptionTable.begin();
-       it != ExceptionEntry.ExceptionTable.end(); it++) {
+  for (auto I = ExceptionEntry.ExceptionTable.begin(),
+          E = ExceptionEntry.ExceptionTable.end();
+     I != E; ++I) {
     // For every symbol that has exception entries, you must start the entries
     // with an initial symbol table index entry
-    W.write<uint32_t>(SymbolIndexMap[it->second.FunctionSymbol]);
+    W.write<uint32_t>(SymbolIndexMap[I->second.FunctionSymbol]);
     if (is64Bit()) {
       // 4-byte padding on 64-bit.
       W.OS.write_zeros(4);
     }
     W.OS.write_zeros(2);
-    for (auto &TrapEntry : it->second.Entries) {
+    for (auto &TrapEntry : I->second.Entries) {
       writeWord(TrapEntry.TrapAddress);
       W.write<uint8_t>(TrapEntry.Lang);
       W.write<uint8_t>(TrapEntry.Reason);

``````````

</details>


https://github.com/llvm/llvm-project/pull/98114