[RISCV] Don't pre-split before the loop in parseNormalizedArchString.

[topperc]

We can extract each extension as we process them without much complexity.

I changed the error message for cases where there are double underscores or a trailing underscore. I think this is an improvement over the previous error.

[llvmbot]

@llvm/pr-subscribers-backend-risc-v

Author: Craig Topper (topperc)

Changes

We can extract each extension as we process them without much complexity.

I changed the error message for cases where there are double underscores or a trailing underscore. I think this is an improvement over the previous error.

---

Full diff: https://github.com/llvm/llvm-project/pull/91684.diff

2 Files Affected:

• (modified) llvm/lib/TargetParser/RISCVISAInfo.cpp (+12-3)
• (modified) llvm/unittests/TargetParser/RISCVISAInfoTest.cpp (+7-2)

diff --git a/llvm/lib/TargetParser/RISCVISAInfo.cpp b/llvm/lib/TargetParser/RISCVISAInfo.cpp
index c553e330a878b..033df27c68781 100644
--- a/llvm/lib/TargetParser/RISCVISAInfo.cpp
+++ b/llvm/lib/TargetParser/RISCVISAInfo.cpp
@@ -451,9 +451,18 @@ RISCVISAInfo::parseNormalizedArchString(StringRef Arch) {
   // Each extension is of the form ${name}${major_version}p${minor_version}
   // and separated by _. Split by _ and then extract the name and version
   // information for each extension.
-  SmallVector<StringRef, 8> Split;
-  Arch.split(Split, '_');
-  for (StringRef Ext : Split) {
+  while (!Arch.empty()) {
+    if (Arch[0] == '_') {
+      if (Arch.size() == 1 || Arch[1] == '_')
+        return createStringError(errc::invalid_argument,
+                                 "extension name missing after separator '_'");
+      Arch = Arch.drop_front();
+    }
+
+    size_t Idx = Arch.find('_');
+    StringRef Ext = Arch.slice(0, Idx);
+    Arch = Arch.slice(Idx, StringRef::npos);
+
     StringRef Prefix, MinorVersionStr;
     std::tie(Prefix, MinorVersionStr) = Ext.rsplit('p');
     if (MinorVersionStr.empty())
diff --git a/llvm/unittests/TargetParser/RISCVISAInfoTest.cpp b/llvm/unittests/TargetParser/RISCVISAInfoTest.cpp
index f9e386a85fea8..7f2d1eb8c0170 100644
--- a/llvm/unittests/TargetParser/RISCVISAInfoTest.cpp
+++ b/llvm/unittests/TargetParser/RISCVISAInfoTest.cpp
@@ -38,12 +38,17 @@ TEST(ParseNormalizedArchString, RejectsInvalidBaseISA) {
 }
 
 TEST(ParseNormalizedArchString, RejectsMalformedInputs) {
-  for (StringRef Input :
-       {"rv64i2p0_", "rv32i2p0__a2p0", "rv64e2p", "rv32i", "rv64ip1"}) {
+  for (StringRef Input : {"rv64e2p", "rv32i", "rv64ip1"}) {
     EXPECT_EQ(
         toString(RISCVISAInfo::parseNormalizedArchString(Input).takeError()),
         "extension lacks version in expected format");
   }
+
+  for (StringRef Input : {"rv64i2p0_", "rv32i2p0__a2p0"}) {
+    EXPECT_EQ(
+        toString(RISCVISAInfo::parseNormalizedArchString(Input).takeError()),
+        "extension name missing after separator '_'");
+  }
 }
 
 TEST(ParseNormalizedArchString, RejectsOnlyVersion) {

[asb]

LGTM