[FileCheck] Avoid capturing group for {{regex}}

[nikic]

For {{regex}} we don't really need a capturing group, and only add it to properly handle cases like {{foo|bar}}. This is problematic, because the use of capturing groups makes our regex implementation slower (we have to go through the "dissect" stage, which can have quadratic complexity).

Unfortunately, our regex implementation does not support non-capturing groups like (?:regex). So instead, avoid adding the group entirely if the regex doesn't contain any alternations.

This causes a slight difference in escaping behavior, where previously it was possible to write {{{{}} and get the same behavior as {{\{\{}}. This will no longer work. I don't think this is a problem, especially as we recently taught update_analyze_test_checks.py to emit {{\{\{}}, so this shouldn't get introduced in any new tests.

For CodeGen/X86/vector-interleaved-store-i16-stride-7.ll (our slowest X86 test) this drops FileCheck time from 6s to 5s (the remainder is spent in a different regex issue). I expect similar speedups in other tests using a lot of {{}}.

[llvmbot]

@llvm/pr-subscribers-testing-tools

@llvm/pr-subscribers-llvm-analysis

Author: Nikita Popov (nikic)

Changes

For {{regex}} we don't really need a capturing group, and only add it to properly handle cases like {{foo|bar}}. This is problematic, because the use of capturing groups makes our regex implementation slower (we have to go through the "dissect" stage, which can have quadratic complexity).

Unfortunately, our regex implementation does not support non-capturing groups like (?:regex). So instead, avoid adding the group entirely if the regex doesn't contain any alternations.

This causes a slight difference in escaping behavior, where previously it was possible to write {{{{}} and get the same behavior as {{\{\{}}. This will no longer work. I don't think this is a problem, especially as we recently taught update_analyze_test_checks.py to emit {{\{\{}}, so this shouldn't get introduced in any new tests.

For CodeGen/X86/vector-interleaved-store-i16-stride-7.ll (our slowest X86 test) this drops FileCheck time from 6s to 5s (the remainder is spent in a different regex issue). I expect similar speedups in other tests using a lot of {{}}.

---

Full diff: https://github.com/llvm/llvm-project/pull/72136.diff

2 Files Affected:

• (modified) llvm/lib/FileCheck/FileCheck.cpp (+7-3)
• (modified) llvm/test/Analysis/ScalarEvolution/different-loops-recs.ll (+18-18)

diff --git a/llvm/lib/FileCheck/FileCheck.cpp b/llvm/lib/FileCheck/FileCheck.cpp
index 49fda8fb63cd36c..bef6dd69fadfdee 100644
--- a/llvm/lib/FileCheck/FileCheck.cpp
+++ b/llvm/lib/FileCheck/FileCheck.cpp
@@ -832,12 +832,16 @@ bool Pattern::parsePattern(StringRef PatternStr, StringRef Prefix,
       // capturing the result for any purpose.  This is required in case the
       // expression contains an alternation like: CHECK:  abc{{x|z}}def.  We
       // want this to turn into: "abc(x|z)def" not "abcx|zdef".
-      RegExStr += '(';
-      ++CurParen;
+      bool HasAlternation = PatternStr.contains('|');
+      if (HasAlternation) {
+        RegExStr += '(';
+        ++CurParen;
+      }
 
       if (AddRegExToRegEx(PatternStr.substr(2, End - 2), CurParen, SM))
         return true;
-      RegExStr += ')';
+      if (HasAlternation)
+        RegExStr += ')';
 
       PatternStr = PatternStr.substr(End + 2);
       continue;
diff --git a/llvm/test/Analysis/ScalarEvolution/different-loops-recs.ll b/llvm/test/Analysis/ScalarEvolution/different-loops-recs.ll
index 349c6bde6991262..4d5f08d41b9ceef 100644
--- a/llvm/test/Analysis/ScalarEvolution/different-loops-recs.ll
+++ b/llvm/test/Analysis/ScalarEvolution/different-loops-recs.ll
@@ -18,17 +18,17 @@ define void @test_00() {
 ; CHECK:       %sum4 = add i32 %sum3, %phi6
 ; CHECK-NEXT:  -->  {159,+,6}<%loop2>
 ; CHECK:       %s1 = add i32 %phi1, %phi4
-; CHECK-NEXT:  -->  {{{{}}73,+,1}<nuw><nsw><%loop1>,+,1}<nw><%loop2>
+; CHECK-NEXT:  -->  {{\{\{}}73,+,1}<nuw><nsw><%loop1>,+,1}<nw><%loop2>
 ; CHECK:       %s2 = add i32 %phi5, %phi2
-; CHECK-NEXT:  -->  {{{{}}57,+,2}<nuw><nsw><%loop1>,+,2}<nw><%loop2>
+; CHECK-NEXT:  -->  {{\{\{}}57,+,2}<nuw><nsw><%loop1>,+,2}<nw><%loop2>
 ; CHECK:       %s3 = add i32 %sum1, %sum3
-; CHECK-NEXT:  -->  {{{{}}130,+,3}<%loop1>,+,3}<%loop2>
+; CHECK-NEXT:  -->  {{\{\{}}130,+,3}<%loop1>,+,3}<%loop2>
 ; CHECK:       %s4 = add i32 %sum4, %sum2
-; CHECK-NEXT:  -->  {{{{}}179,+,6}<%loop1>,+,6}<%loop2>
+; CHECK-NEXT:  -->  {{\{\{}}179,+,6}<%loop1>,+,6}<%loop2>
 ; CHECK:       %s5 = add i32 %phi3, %sum3
-; CHECK-NEXT:  -->  {{{{}}122,+,3}<nuw><nsw><%loop1>,+,3}<%loop2>
+; CHECK-NEXT:  -->  {{\{\{}}122,+,3}<nuw><nsw><%loop1>,+,3}<%loop2>
 ; CHECK:       %s6 = add i32 %sum2, %phi6
-; CHECK-NEXT:  -->  {{{{}}63,+,6}<%loop1>,+,3}<nw><%loop2>
+; CHECK-NEXT:  -->  {{\{\{}}63,+,6}<%loop1>,+,3}<nw><%loop2>
 
 entry:
   br label %loop1
@@ -359,17 +359,17 @@ define void @test_06() {
 
 ; CHECK-LABEL: Classifying expressions for: @test_06
 ; CHECK:       %s1 = add i32 %phi1, %phi2
-; CHECK-NEXT:  -->  {{{{}}30,+,1}<nuw><nsw><%loop1>,+,2}<nw><%loop2>
+; CHECK-NEXT:  -->  {{\{\{}}30,+,1}<nuw><nsw><%loop1>,+,2}<nw><%loop2>
 ; CHECK:       %s2 = add i32 %phi2, %phi1
-; CHECK-NEXT:  -->  {{{{}}30,+,1}<nuw><nsw><%loop1>,+,2}<nw><%loop2>
+; CHECK-NEXT:  -->  {{\{\{}}30,+,1}<nuw><nsw><%loop1>,+,2}<nw><%loop2>
 ; CHECK:       %s3 = add i32 %phi1, %phi3
-; CHECK-NEXT:  -->  {{{{}}40,+,1}<nuw><nsw><%loop1>,+,3}<nw><%loop3>
+; CHECK-NEXT:  -->  {{\{\{}}40,+,1}<nuw><nsw><%loop1>,+,3}<nw><%loop3>
 ; CHECK:       %s4 = add i32 %phi3, %phi1
-; CHECK-NEXT:  -->  {{{{}}40,+,1}<nuw><nsw><%loop1>,+,3}<nw><%loop3>
+; CHECK-NEXT:  -->  {{\{\{}}40,+,1}<nuw><nsw><%loop1>,+,3}<nw><%loop3>
 ; CHECK:       %s5 = add i32 %phi2, %phi3
-; CHECK-NEXT:  -->  {{{{}}50,+,2}<nuw><nsw><%loop2>,+,3}<nw><%loop3>
+; CHECK-NEXT:  -->  {{\{\{}}50,+,2}<nuw><nsw><%loop2>,+,3}<nw><%loop3>
 ; CHECK:       %s6 = add i32 %phi3, %phi2
-; CHECK-NEXT:  -->  {{{{}}50,+,2}<nuw><nsw><%loop2>,+,3}<nw><%loop3>
+; CHECK-NEXT:  -->  {{\{\{}}50,+,2}<nuw><nsw><%loop2>,+,3}<nw><%loop3>
 
 entry:
   br label %loop1
@@ -411,17 +411,17 @@ define void @test_07() {
 
 ; CHECK-LABEL: Classifying expressions for: @test_07
 ; CHECK:       %s1 = add i32 %phi1, %phi2
-; CHECK-NEXT:  -->  {{{{}}30,+,1}<nuw><nsw><%loop1>,+,2}<nw><%loop2>
+; CHECK-NEXT:  -->  {{\{\{}}30,+,1}<nuw><nsw><%loop1>,+,2}<nw><%loop2>
 ; CHECK:       %s2 = add i32 %phi2, %phi1
-; CHECK-NEXT:  -->  {{{{}}30,+,1}<nuw><nsw><%loop1>,+,2}<nw><%loop2>
+; CHECK-NEXT:  -->  {{\{\{}}30,+,1}<nuw><nsw><%loop1>,+,2}<nw><%loop2>
 ; CHECK:       %s3 = add i32 %phi1, %phi3
-; CHECK-NEXT:  -->  {{{{}}40,+,3}<nuw><nsw><%loop3>,+,1}<nw><%loop1>
+; CHECK-NEXT:  -->  {{\{\{}}40,+,3}<nuw><nsw><%loop3>,+,1}<nw><%loop1>
 ; CHECK:       %s4 = add i32 %phi3, %phi1
-; CHECK-NEXT:  -->  {{{{}}40,+,3}<nuw><nsw><%loop3>,+,1}<nw><%loop1>
+; CHECK-NEXT:  -->  {{\{\{}}40,+,3}<nuw><nsw><%loop3>,+,1}<nw><%loop1>
 ; CHECK:       %s5 = add i32 %phi2, %phi3
-; CHECK-NEXT:  -->  {{{{}}50,+,3}<nuw><nsw><%loop3>,+,2}<nw><%loop2>
+; CHECK-NEXT:  -->  {{\{\{}}50,+,3}<nuw><nsw><%loop3>,+,2}<nw><%loop2>
 ; CHECK:       %s6 = add i32 %phi3, %phi2
-; CHECK-NEXT:  -->  {{{{}}50,+,3}<nuw><nsw><%loop3>,+,2}<nw><%loop2>
+; CHECK-NEXT:  -->  {{\{\{}}50,+,3}<nuw><nsw><%loop3>,+,2}<nw><%loop2>
 
 entry:
   br label %loop3

[tstellar]

LGTM.