[llvm] [RISCV] Don't crash in RISCVMergeBaseOffset if INLINE_ASM uses address register in a non-memory constraint. (PR #100790)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

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

Author: Craig Topper (topperc)

<details>
<summary>Changes</summary>

If the register is used by a non-memory constraint we should disable the fold. Otherwise, we may leave CommonOffset unassigned.

Fixes #<!-- -->100779.

---
Full diff: https://github.com/llvm/llvm-project/pull/100790.diff


2 Files Affected:

- (modified) llvm/lib/Target/RISCV/RISCVMergeBaseOffset.cpp (+9-1) 
- (modified) llvm/test/CodeGen/RISCV/inline-asm-mem-constraint.ll (+50) 


``````````diff
diff --git a/llvm/lib/Target/RISCV/RISCVMergeBaseOffset.cpp b/llvm/lib/Target/RISCV/RISCVMergeBaseOffset.cpp
index fecc83a821f42..b6ac3384e7d3e 100644
--- a/llvm/lib/Target/RISCV/RISCVMergeBaseOffset.cpp
+++ b/llvm/lib/Target/RISCV/RISCVMergeBaseOffset.cpp
@@ -429,8 +429,16 @@ bool RISCVMergeBaseOffsetOpt::foldIntoMemoryOps(MachineInstr &Hi,
         NumOps = Flags.getNumOperandRegisters();
 
         // Memory constraints have two operands.
-        if (NumOps != 2 || !Flags.isMemKind())
+        if (NumOps != 2 || !Flags.isMemKind()) {
+          // If the register is used by something other than a memory contraint,
+          // we should not fold.
+          for (unsigned J = 0; J < NumOps; ++J) {
+            const MachineOperand &MO = UseMI.getOperand(I + 1 + J);
+            if (MO.isReg() && MO.getReg() == DestReg)
+              return false;
+          }
           continue;
+        }
 
         // We can't do this for constraint A because AMO instructions don't have
         // an immediate offset field.
diff --git a/llvm/test/CodeGen/RISCV/inline-asm-mem-constraint.ll b/llvm/test/CodeGen/RISCV/inline-asm-mem-constraint.ll
index 52d0dabf18839..6666d92feaac2 100644
--- a/llvm/test/CodeGen/RISCV/inline-asm-mem-constraint.ll
+++ b/llvm/test/CodeGen/RISCV/inline-asm-mem-constraint.ll
@@ -2252,3 +2252,53 @@ label:
   call void asm "lw zero, $0", "*A"(ptr elementtype(i32) getelementptr (i8, ptr blockaddress(@constraint_A_with_local_3, %label), i32 2000))
   ret void
 }
+
+ at _ZN5repro9MY_BUFFER17hb0f674501d5980a6E = external global <{ [16 x i8] }>
+
+; Address is not used by a memory constraint.
+define void @should_not_fold() {
+; RV32I-LABEL: should_not_fold:
+; RV32I:       # %bb.0: # %start
+; RV32I-NEXT:    .cfi_def_cfa_offset 0
+; RV32I-NEXT:    lui a0, %hi(_ZN5repro9MY_BUFFER17hb0f674501d5980a6E)
+; RV32I-NEXT:    addi a0, a0, %lo(_ZN5repro9MY_BUFFER17hb0f674501d5980a6E)
+; RV32I-NEXT:    #APP
+; RV32I-NEXT:    ecall
+; RV32I-NEXT:    #NO_APP
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: should_not_fold:
+; RV64I:       # %bb.0: # %start
+; RV64I-NEXT:    .cfi_def_cfa_offset 0
+; RV64I-NEXT:    lui a0, %hi(_ZN5repro9MY_BUFFER17hb0f674501d5980a6E)
+; RV64I-NEXT:    addi a0, a0, %lo(_ZN5repro9MY_BUFFER17hb0f674501d5980a6E)
+; RV64I-NEXT:    #APP
+; RV64I-NEXT:    ecall
+; RV64I-NEXT:    #NO_APP
+; RV64I-NEXT:    ret
+;
+; RV32I-MEDIUM-LABEL: should_not_fold:
+; RV32I-MEDIUM:       # %bb.0: # %start
+; RV32I-MEDIUM-NEXT:    .cfi_def_cfa_offset 0
+; RV32I-MEDIUM-NEXT:  .Lpcrel_hi39:
+; RV32I-MEDIUM-NEXT:    auipc a0, %pcrel_hi(_ZN5repro9MY_BUFFER17hb0f674501d5980a6E)
+; RV32I-MEDIUM-NEXT:    addi a0, a0, %pcrel_lo(.Lpcrel_hi39)
+; RV32I-MEDIUM-NEXT:    #APP
+; RV32I-MEDIUM-NEXT:    ecall
+; RV32I-MEDIUM-NEXT:    #NO_APP
+; RV32I-MEDIUM-NEXT:    ret
+;
+; RV64I-MEDIUM-LABEL: should_not_fold:
+; RV64I-MEDIUM:       # %bb.0: # %start
+; RV64I-MEDIUM-NEXT:    .cfi_def_cfa_offset 0
+; RV64I-MEDIUM-NEXT:  .Lpcrel_hi39:
+; RV64I-MEDIUM-NEXT:    auipc a0, %pcrel_hi(_ZN5repro9MY_BUFFER17hb0f674501d5980a6E)
+; RV64I-MEDIUM-NEXT:    addi a0, a0, %pcrel_lo(.Lpcrel_hi39)
+; RV64I-MEDIUM-NEXT:    #APP
+; RV64I-MEDIUM-NEXT:    ecall
+; RV64I-MEDIUM-NEXT:    #NO_APP
+; RV64I-MEDIUM-NEXT:    ret
+start:
+  %0 = tail call ptr asm sideeffect alignstack "ecall", "=&{x10},0,~{vtype},~{vl},~{vxsat},~{vxrm},~{memory}"(ptr @_ZN5repro9MY_BUFFER17hb0f674501d5980a6E)
+  ret void
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/100790