[WebAssembly] Enable simd128 when relaxed-simd is set in AsmPrinter

[aheejin]

Even though in Subtarget we defined SIMDLevel as a number so hasRelaxedSIMD automatically means hasSIMD128,

llvm-project/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h

Lines 36 to 40 in 0caf0c9

	enum SIMDEnum {
	NoSIMD,
	SIMD128,
	RelaxedSIMD,
	} SIMDLevel = NoSIMD;

llvm-project/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h

Line 107 in 0caf0c9

bool hasSIMD128() const { return SIMDLevel >= SIMD128; }

specifying only relaxed-simd feature on a program that needs simd128 instructions to compile fails, because of this query in AsmPrinter:

llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp

Lines 644 to 645 in d0d05ae

	WebAssembly_MC::verifyInstructionPredicates(MI->getOpcode(),
	Subtarget->getFeatureBits());

This verifyInstructionPredicates function (and other functions called by this function) is generated by
https://github.com/llvm/llvm-project/blob/main/llvm/utils/TableGen/InstrInfoEmitter.cpp, and looks like this (you can check it in the lib/Target/WebAssembly/WebAssemblyGenInstrInfo.inc in your build directory):

void verifyInstructionPredicates(
    unsigned Opcode, const FeatureBitset &Features) {
  FeatureBitset AvailableFeatures = computeAvailableFeatures(Features);
  FeatureBitset RequiredFeatures = computeRequiredFeatures(Opcode);
  FeatureBitset MissingFeatures =
      (AvailableFeatures & RequiredFeatures) ^
      RequiredFeatures;
  ...
}

And computeAvailableFeatures is just a set query, like this:

inline FeatureBitset computeAvailableFeatures(const FeatureBitset &FB) {
  FeatureBitset Features;
  if (FB[WebAssembly::FeatureAtomics])
    Features.set(Feature_HasAtomicsBit);
  if (FB[WebAssembly::FeatureBulkMemory])
    Features.set(Feature_HasBulkMemoryBit);
  if (FB[WebAssembly::FeatureExceptionHandling])
    Features.set(Feature_HasExceptionHandlingBit);
  ...

So this is how currently HasSIMD128 is defined:

llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td

Lines 79 to 81 in 0caf0c9

	def HasSIMD128 :
	Predicate<"Subtarget->hasSIMD128()">,
	AssemblerPredicate<(all_of FeatureSIMD128), "simd128">;

The things being checked in this computeAvailableFeatures, and in turn in AsmPrinter, are AssemblerPredicates. These only check which bits are set in the features set and are different from Predicates, which can call Subtarget functions like Subtarget->hasSIMD128().

But apparently we can use all_of and any_of directives in AssemblerPredicate, and we can make simd128's AssemblerPredicate set in relaxed-simd is set by the condition as an 'or' of the two.

Fixes #98502.

[llvmbot]

@llvm/pr-subscribers-backend-webassembly

Author: Heejin Ahn (aheejin)

Changes

Even though in Subtarget we defined SIMDLevel as a number so hasRelaxedSIMD automatically means hasSIMD128,

llvm-project/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h

Lines 36 to 40 in 0caf0c9

	enum SIMDEnum {
	NoSIMD,
	SIMD128,
	RelaxedSIMD,
	} SIMDLevel = NoSIMD;

llvm-project/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h

Line 107 in 0caf0c9

bool hasSIMD128() const { return SIMDLevel >= SIMD128; }

specifying only relaxed-simd feature on a program that needs simd128 instructions to compile fails, because of this query in AsmPrinter:

llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp

Lines 644 to 645 in d0d05ae

	WebAssembly_MC::verifyInstructionPredicates(MI->getOpcode(),
	Subtarget->getFeatureBits());

This verifyInstructionPredicates function (and other functions called by this function) is generated by
https://github.com/llvm/llvm-project/blob/main/llvm/utils/TableGen/InstrInfoEmitter.cpp, and looks like this (you can check it in the
lib/Target/WebAssembly/WebAssemblyGenInstrInfo.inc in your build directory):

void verifyInstructionPredicates(
    unsigned Opcode, const FeatureBitset &Features) {
  FeatureBitset AvailableFeatures = computeAvailableFeatures(Features);
  FeatureBitset RequiredFeatures = computeRequiredFeatures(Opcode);
  FeatureBitset MissingFeatures =
      (AvailableFeatures & RequiredFeatures) ^
      RequiredFeatures;
  ...
}

And computeAvailableFeatures there is just a set query, like this:

inline FeatureBitset computeAvailableFeatures(const FeatureBitset &FB) {
  FeatureBitset Features;
  if (FB[WebAssembly::FeatureAtomics])
    Features.set(Feature_HasAtomicsBit);
  if (FB[WebAssembly::FeatureBulkMemory])
    Features.set(Feature_HasBulkMemoryBit);
  if (FB[WebAssembly::FeatureExceptionHandling])
    Features.set(Feature_HasExceptionHandlingBit);
  ...

So this is how currently HasSIMD128 is defined:

llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td

Lines 79 to 81 in 0caf0c9

	def HasSIMD128 :
	Predicate<"Subtarget->hasSIMD128()">,
	AssemblerPredicate<(all_of FeatureSIMD128), "simd128">;

The things being checked in this computeAvailableFeatures, and in turn in AsmPrinter, are AssemblerPredicates. These only check which bits are set in the features set and are different from Predicates, which can call Subtarget functions like Subtarget->hasSIMD128().

But apparently we can use all_of and any_of directives in AssemblerPredicate, and we can make simd128's AssemblerPredicate set in relaxed-simd is set by the condition as an 'or' of the two.

Fixes #98502.

---

Full diff: https://github.com/llvm/llvm-project/pull/99803.diff

2 Files Affected:

• (modified) llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td (+1-1)
• (added) llvm/test/CodeGen/WebAssembly/simd-asm-pred.ll (+24)

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td
index 3d37eb2fa27bc..bb36ce7650183 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td
@@ -78,7 +78,7 @@ def HasSignExt :
 
 def HasSIMD128 :
     Predicate<"Subtarget->hasSIMD128()">,
-    AssemblerPredicate<(all_of FeatureSIMD128), "simd128">;
+    AssemblerPredicate<(any_of FeatureSIMD128, FeatureRelaxedSIMD), "simd128">;
 
 def HasTailCall :
     Predicate<"Subtarget->hasTailCall()">,
diff --git a/llvm/test/CodeGen/WebAssembly/simd-asm-pred.ll b/llvm/test/CodeGen/WebAssembly/simd-asm-pred.ll
new file mode 100644
index 0000000000000..f022c3e745125
--- /dev/null
+++ b/llvm/test/CodeGen/WebAssembly/simd-asm-pred.ll
@@ -0,0 +1,24 @@
+; RUN: llc < %s -verify-machineinstrs -mattr=+relaxed-simd | FileCheck %s
+
+; Test that setting "relaxed-simd" target feature set also implies 'simd128' in
+; AssemblerPredicate, which is used to verify instructions in AsmPrinter.
+
+target triple = "wasm32-unknown-unknown"
+
+declare <2 x i64> @llvm.wasm.relaxed.laneselect.v2i64(<2 x i64>, <2 x i64>, <2 x i64>)
+
+; The compiled result of this function uses LOCAL_GET_V128, which is predicated
+; on the 'simd128' feature. We should be able to compile this when only
+; 'relaxed-simd' is set, which implies 'simd128'.
+define <2 x i64> @test(<2 x i64>, <2 x i64>, <2 x i64>) #0 {
+; CHECK-LABEL: test:
+; CHECK:         .functype  test (v128, v128, v128) -> (v128)
+; CHECK-NEXT:  # %bb.0:
+; CHECK-NEXT:    local.get  0
+; CHECK-NEXT:    local.get  1
+; CHECK-NEXT:    local.get  2
+; CHECK-NEXT:    i64x2.relaxed_laneselect
+start:
+  %_4 = tail call <2 x i64> @llvm.wasm.relaxed.laneselect.v2i64(<2 x i64> %0, <2 x i64> %1, <2 x i64> %2) #3
+  ret <2 x i64> %_4
+}

[aheejin]

cc @alexcrichton

[tlively]

Thanks, @aheejin!

[aheejin]

Will merge this; the CI failure doesn't seem to be related.