[RISCV] Only set Zca flag for EF_RISCV_RVC in ELFObjectFileBase::getRISCVFeatures(). (#80928)

This code appears to be a hack to set the features to include compressed
instructions if the ELF EFLAGS flags bit is present, but the ELF
attribute for the ISA string is no present or not accurate.

We can't remove the hack because llvm-mc doesn't create ELF attributes
by default so a lot of tests fail to disassembler properly. Using clang
as the assembler does set the attributes.

This patch changes the hack to only set Zca since that is the minimum
implied by the flag. Setting anything else potentially conflicts with
the ISA string containing Zcmp or Zcmt.

JITLink also needs to be updated to recognize Zca in addition to C.

Author: topperc

Diff for: llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp

@@ -525,7 +525,8 @@ static RelaxAux initRelaxAux(LinkGraph &G) {
   RelaxAux Aux;
   Aux.Config.IsRV32 = G.getTargetTriple().isRISCV32();
   const auto &Features = G.getFeatures().getFeatures();
-  Aux.Config.HasRVC = llvm::is_contained(Features, "+c");
+  Aux.Config.HasRVC = llvm::is_contained(Features, "+c") ||
+                      llvm::is_contained(Features, "+zca");
 
   for (auto &S : G.sections()) {
     if (!shouldRelax(S))

Diff for: llvm/lib/Object/ELFObjectFile.cpp

@@ -292,7 +292,7 @@ Expected<SubtargetFeatures> ELFObjectFileBase::getRISCVFeatures() const {
   unsigned PlatformFlags = getPlatformFlags();
 
   if (PlatformFlags & ELF::EF_RISCV_RVC) {
-    Features.AddFeature("c");
+    Features.AddFeature("zca");
   }
 
   RISCVAttributeParser Attributes;

Diff for: llvm/test/ExecutionEngine/JITLink/RISCV/ELF_relax_align_rvc.s

@@ -10,6 +10,16 @@
 # RUN:     -slab-allocate 100Kb -slab-address 0x0 -slab-page-size 4096 \
 # RUN:     -check %s %t.rv64
 
+# RUN: llvm-mc -filetype=obj -triple=riscv32 -mattr=+relax,+zca %s -o %t.rv32zca
+# RUN: llvm-jitlink -noexec \
+# RUN:     -slab-allocate 100Kb -slab-address 0x0 -slab-page-size 4096 \
+# RUN:     -check %s %t.rv32zca
+
+# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+zca %s -o %t.rv64zca
+# RUN: llvm-jitlink -noexec \
+# RUN:     -slab-allocate 100Kb -slab-address 0x0 -slab-page-size 4096 \
+# RUN:     -check %s %t.rv64zca
+
     .globl main,align2,align4,align8,align16,align32
     .type  main,@function
 main:

Diff for: llvm/test/ExecutionEngine/JITLink/RISCV/ELF_relax_call_boundary.s

@@ -11,6 +11,16 @@
 # RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
 # RUN:     -check %s %t.rv64
 
+# RUN: llvm-mc -filetype=obj -triple=riscv32 -mattr=+relax,+zca %s -o %t.rv32zca
+# RUN: llvm-jitlink -noexec \
+# RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
+# RUN:     -check %s %t.rv32zca
+
+# RUN: llvm-mc -filetype=obj -triple=riscv64 -mattr=+relax,+zca %s -o %t.rv64zca
+# RUN: llvm-jitlink -noexec \
+# RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
+# RUN:     -check %s %t.rv64zca
+
         .globl main
         .type main,@function
 main:

Diff for: llvm/test/ExecutionEngine/JITLink/RISCV/ELF_relax_call_rvc.s

@@ -9,6 +9,26 @@
 # RUN:     -debug-only=jitlink -check %s -check-name=jitlink-check-rv32 %t.rv32 \
 # RUN:     2>&1 | FileCheck -check-prefix=CHECK-RV32 %s
 
+# RUN: llvm-mc -triple=riscv64 -mattr=+relax,+c -filetype=obj -o %t.rv64 %s
+# RUN: llvm-jitlink -noexec \
+# RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
+# RUN:     -debug-only=jitlink -check %s %t.rv64 \
+# RUN:     2>&1 | FileCheck %s
+# RUN: llvm-jitlink -noexec \
+# RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
+# RUN:     -debug-only=jitlink -check %s -check-name=jitlink-check-rv64 %t.rv64 \
+# RUN:     2>&1 | FileCheck -check-prefix=CHECK-RV64 %s
+
+# RUN: llvm-mc -triple=riscv32 -mattr=+relax,+zca -filetype=obj -o %t.rv32zca %s
+# RUN: llvm-jitlink -noexec \
+# RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
+# RUN:     -debug-only=jitlink -check %s %t.rv32zca \
+# RUN:    2>&1 | FileCheck %s
+# RUN: llvm-jitlink -noexec \
+# RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
+# RUN:     -debug-only=jitlink -check %s -check-name=jitlink-check-rv32 %t.rv32zca \
+# RUN:     2>&1 | FileCheck -check-prefix=CHECK-RV32 %s
+
 # RUN: llvm-mc -triple=riscv64 -mattr=+relax,+c -filetype=obj -o %t.rv64 %s
 # RUN: llvm-jitlink -noexec \
 # RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \