[AMDGPU] Fix crash for inline-asm inputs of type MVT::Other

[ro-i]

Sorry, @arsenm, could you approve again, please? I accidentally merged #153401 into #149308, which I, of course, did not meant to do because that makes that PR harder to review since it's not clear anymore to which PR which changes belong.

[llvmbot]

@llvm/pr-subscribers-backend-amdgpu

Author: Robert Imschweiler (ro-i)

Changes

Sorry, @arsenm, could you approve again, please? I accidentally merged #153401 into #149308, which I, of course, did not meant to do because that makes that PR harder to review since it's not clear anymore to which PR which changes belong.

---

Full diff: https://github.com/llvm/llvm-project/pull/153425.diff

2 Files Affected:

• (modified) llvm/lib/Target/AMDGPU/SIISelLowering.cpp (+5)
• (modified) llvm/test/CodeGen/AMDGPU/inlineasm-illegal-type.ll (+6)

diff --git a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
index 2e76225bbc542..f58fde421f77d 100644
--- a/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/SIISelLowering.cpp
@@ -16894,6 +16894,11 @@ SITargetLowering::getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI_,
 
   const TargetRegisterClass *RC = nullptr;
   if (Constraint.size() == 1) {
+    // Check if we cannot determine the bit size of the given value type.  This
+    // can happen, for example, in this situation where we have an empty struct
+    // (size 0): `call void asm "", "v"({} poison)`-
+    if (VT == MVT::Other)
+      return TargetLowering::getRegForInlineAsmConstraint(TRI, Constraint, VT);
     const unsigned BitWidth = VT.getSizeInBits();
     switch (Constraint[0]) {
     default:
diff --git a/llvm/test/CodeGen/AMDGPU/inlineasm-illegal-type.ll b/llvm/test/CodeGen/AMDGPU/inlineasm-illegal-type.ll
index 9f7f228297d47..535e02cf80c2c 100644
--- a/llvm/test/CodeGen/AMDGPU/inlineasm-illegal-type.ll
+++ b/llvm/test/CodeGen/AMDGPU/inlineasm-illegal-type.ll
@@ -18,6 +18,12 @@ define amdgpu_kernel void @v_input_output_i8() {
   ret void
 }
 
+; GCN: error: couldn't allocate input reg for constraint 'v'
+define amdgpu_kernel void @v_input_empty_struct() {
+  call void asm "", "v"({} poison)
+  ret void
+}
+
 ; SICI: error: couldn't allocate output register for constraint 's'
 ; SICI: error: couldn't allocate input reg for constraint 's'
 ; VI-NOT: error