[PATCH] D91710: [SelDAGBuilder] Do not require simple VTs for constraints.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: efriedma, t.p.northover, craig.topper, arsenm, nickdesaulniers.
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Herald added a subscriber: wdng.

In some cases, the values passed to `asm sideeffect` calls cannot be
mapped directly to simple MVTs. Currently, we crash in the backend if
that happens. An example can be found in the @test_vector_too_large_r_m
test case, where we pass <9 x float> vectors. In practice, this can
happen in cases like the simple C example below.

using vec = float __attribute__((ext_vector_type(9)));
void f1 (vec m) {

  asm volatile("" : "+r,m"(m) : : "memory");

}

One case that use "+r,m" constraints for arbitrary data types in
practice is google-benchmark's DoNotOptimize.

This patch updates visitInlineAsm so that it use MVT::Other for
constraints with complex VTs. It looks like the rest of the backend
correctly deals with that and properly legalizes the type.

And we still report an error if there are no registers to satisfy the
constraint.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D91710

Files:
  llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
  llvm/test/CodeGen/AArch64/arm64-inline-asm.ll
  llvm/test/CodeGen/AArch64/inlineasm-illegal-type.ll


Index: llvm/test/CodeGen/AArch64/inlineasm-illegal-type.ll
===================================================================
--- llvm/test/CodeGen/AArch64/inlineasm-illegal-type.ll
+++ llvm/test/CodeGen/AArch64/inlineasm-illegal-type.ll
@@ -2,6 +2,8 @@
 
 ; CHECK: error: couldn't allocate output register for constraint '{d0}'
 ; CHECK: error: couldn't allocate output register for constraint 'w'
+; CHECK: error: couldn't allocate input reg for constraint 'w'
+; CHECK: error: couldn't allocate input reg for constraint 'w'
 
 define hidden double @test1(double %xx) local_unnamed_addr #0 {
 entry:
@@ -15,3 +17,16 @@
   ret double %0
 }
 
+define void @test_vector_too_large(<8 x float>* nocapture readonly %0) {
+entry:
+  %m = load <8 x float>, <8 x float>* %0, align 16
+  tail call void asm sideeffect "fadd.4s v4, v4, $0", "w,~{memory}"(<8 x float> %m)
+  ret void
+}
+
+define void @test_vector_no_mvt(<9 x float>* nocapture readonly %0) {
+entry:
+  %m = load <9 x float>, <9 x float>* %0, align 16
+  tail call void asm sideeffect "fadd.4s v4, v4, $0", "w,~{memory}"(<9 x float> %m)
+  ret void
+}
Index: llvm/test/CodeGen/AArch64/arm64-inline-asm.ll
===================================================================
--- llvm/test/CodeGen/AArch64/arm64-inline-asm.ll
+++ llvm/test/CodeGen/AArch64/arm64-inline-asm.ll
@@ -282,3 +282,18 @@
   tail call void asm sideeffect "fmla v2.4s, v0.4s, v1.s[$0]", "I"(i32 1) #1
   ret void
 }
+define void @test_vector_too_large_r_m(<9 x float>* nocapture readonly %0) {
+; CHECK-LABEL: test_vector_too_large_r_m
+; CHECK:      ldr [[S:s[0-9]+]], [x0, #32]
+; CHECK-DAG:  ldp [[Q0:q[0-9]+]], [[Q1:q[0-9]+]], [x0]
+; CHECK:      str [[S]], [sp, #32]
+; CHECK-DAG   stp [[Q0]], [[Q1]], [sp]
+; CHECK:     ; InlineAsm Start
+;
+entry:
+  %m.addr = alloca <9 x float>, align 16
+  %m = load <9 x float>, <9 x float>* %0, align 16
+  store <9 x float> %m, <9 x float>* %m.addr, align 16
+  call void asm sideeffect "", "=*r|m,0,~{memory}"(<9 x float>* nonnull %m.addr, <9 x float> %m)
+  ret void
+}
Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -8087,10 +8087,9 @@
         OpInfo.CallOperand = getValue(OpInfo.CallOperandVal);
       }
 
-      OpInfo.ConstraintVT =
-          OpInfo
-              .getCallOperandValEVT(*DAG.getContext(), TLI, DAG.getDataLayout())
-              .getSimpleVT();
+      EVT VT = OpInfo.getCallOperandValEVT(*DAG.getContext(), TLI,
+                                           DAG.getDataLayout());
+      OpInfo.ConstraintVT = VT.isSimple() ? VT.getSimpleVT() : MVT::Other;
     } else if (OpInfo.Type == InlineAsm::isOutput && !OpInfo.isIndirect) {
       // The return value of the call is this value.  As such, there is no
       // corresponding argument.


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