[clang] [llvm] [RISCV][VCIX] Add vcix_state to GNU inline assembly register set (PR #106914)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Brandon Wu (4vtomat)

<details>
<summary>Changes</summary>

[RISCV][VCIX] Add vcix_state to GNU inline assembly register set

 Resolved https://github.com/llvm/llvm-project/issues/106700.
 This enables inline asm to have vcix_state to be a clobbered register
 thus disable reordering between VCIX intrinsics and inline asm.


---
Full diff: https://github.com/llvm/llvm-project/pull/106914.diff


3 Files Affected:

- (modified) clang/lib/Basic/Targets/RISCV.cpp (+1-1) 
- (modified) llvm/lib/Target/RISCV/RISCVRegisterInfo.td (+5-1) 
- (added) llvm/test/CodeGen/RISCV/inline-asm-xsfvcp.ll (+22) 


``````````diff
diff --git a/clang/lib/Basic/Targets/RISCV.cpp b/clang/lib/Basic/Targets/RISCV.cpp
index b89109e7725d44..da6ecfb4e4022b 100644
--- a/clang/lib/Basic/Targets/RISCV.cpp
+++ b/clang/lib/Basic/Targets/RISCV.cpp
@@ -44,7 +44,7 @@ ArrayRef<const char *> RISCVTargetInfo::getGCCRegNames() const {
       "v24", "v25", "v26", "v27", "v28", "v29", "v30", "v31",
 
       // CSRs
-      "fflags", "frm", "vtype", "vl", "vxsat", "vxrm"
+      "fflags", "frm", "vtype", "vl", "vxsat", "vxrm", "vcix_state"
     };
   // clang-format on
   return llvm::ArrayRef(GCCRegNames);
diff --git a/llvm/lib/Target/RISCV/RISCVRegisterInfo.td b/llvm/lib/Target/RISCV/RISCVRegisterInfo.td
index 4d5c0a7bef9416..03f05c0baea3b0 100644
--- a/llvm/lib/Target/RISCV/RISCVRegisterInfo.td
+++ b/llvm/lib/Target/RISCV/RISCVRegisterInfo.td
@@ -664,5 +664,9 @@ def FRM    : RISCVReg<0, "frm">;
 // Shadow Stack register
 def SSP    : RISCVReg<0, "ssp">;
 
-// Dummy VCIX state register
+// Dummy VCIX state register and its register class
 def VCIX_STATE : RISCVReg<0, "vcix_state">;
+def : RISCVRegisterClass<[XLenVT], 32, (add VCIX_STATE)> {
+  let RegInfos = XLenRI;
+  let isAllocatable = 0;
+}
diff --git a/llvm/test/CodeGen/RISCV/inline-asm-xsfvcp.ll b/llvm/test/CodeGen/RISCV/inline-asm-xsfvcp.ll
new file mode 100644
index 00000000000000..0013461d873281
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/inline-asm-xsfvcp.ll
@@ -0,0 +1,22 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: sed 's/iXLen/i32/g' %s | llc -mtriple=riscv32 -mattr=+v,+xsfvcp \
+; RUN:   -verify-machineinstrs | FileCheck %s --check-prefixes=CHECK
+; RUN: sed 's/iXLen/i64/g' %s | llc -mtriple=riscv64 -mattr=+v,+xsfvcp \
+; RUN:   -verify-machineinstrs | FileCheck %s --check-prefixes=CHECK
+
+; VCIX instructions can not reorder between each other.
+define void @test_reorder(<vscale x 1 x i64> %vreg) {
+; CHECK-LABEL: test_reorder:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetivli zero, 0, e64, m1, ta, ma
+; CHECK-NEXT:    sf.vc.iv 0, 0, v8, 0
+; CHECK-NEXT:    #APP
+; CHECK-NEXT:    sf.vc.vv 3, 0, v8, v8
+; CHECK-EMPTY:
+; CHECK-NEXT:    #NO_APP
+; CHECK-NEXT:    ret
+entry:
+  call void @llvm.riscv.sf.vc.iv.se.iXLen.nxv1i64.iXLen.iXLen(iXLen 0, iXLen 0, <vscale x 1 x i64> %vreg, iXLen 0, iXLen 0)
+  call iXLen asm sideeffect "sf.vc.vv 0x3, 0x0, $1, $1;", "=r,^vr,~{memory},~{vl},~{vcix_state}"(<vscale x 1 x i64> %vreg)
+  ret void
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/106914