compiler: move LLVM math builtin support into the compiler

This simplifies src/runtime/math.go, which I eventually want to remove
entirely by moving the given functionality into the compiler.

compiler/compiler.go

@@ -23,7 +23,7 @@ import (
 // Version of the compiler pacakge. Must be incremented each time the compiler
 // package changes in a way that affects the generated LLVM module.
 // This version is independent of the TinyGo version number.
-const Version = 12 // last change: implement syscall.rawSyscallNoError
+const Version = 13 // last change: implement LLVM math builtins in the compiler
 
 func init() {
 	llvm.InitializeAllTargets()
@@ -1298,6 +1298,11 @@ func (b *builder) createFunctionCall(instr *ssa.CallCommon) (llvm.Value, error)
 			return b.createMemoryCopyCall(fn, instr.Args)
 		case name == "runtime.memzero":
 			return b.createMemoryZeroCall(instr.Args)
+		case name == "math.Ceil" || name == "math.Floor" || name == "math.Sqrt" || name == "math.Trunc":
+			result, ok := b.createMathOp(instr)
+			if ok {
+				return result, nil
+			}
 		case name == "device.Asm" || name == "device/arm.Asm" || name == "device/arm64.Asm" || name == "device/avr.Asm" || name == "device/riscv.Asm":
 			return b.createInlineAsm(instr.Args)
 		case name == "device.AsmFull" || name == "device/arm.AsmFull" || name == "device/arm64.AsmFull" || name == "device/avr.AsmFull" || name == "device/riscv.AsmFull":

compiler/compiler_test.go

@@ -48,6 +48,8 @@ func TestCompiler(t *testing.T) {
 		{"pragma.go", ""},
 		{"goroutine.go", "wasm"},
 		{"goroutine.go", "cortex-m-qemu"},
+		{"intrinsics.go", "cortex-m-qemu"},
+		{"intrinsics.go", "wasm"},
 	}
 
 	for _, tc := range tests {

compiler/intrinsics.go

@@ -48,3 +48,57 @@ func (b *builder) createMemoryZeroCall(args []ssa.Value) (llvm.Value, error) {
 	b.CreateCall(llvmFn, params, "")
 	return llvm.Value{}, nil
 }
+
+var mathToLLVMMapping = map[string]string{
+	"math.Sqrt":  "llvm.sqrt.f64",
+	"math.Floor": "llvm.floor.f64",
+	"math.Ceil":  "llvm.ceil.f64",
+	"math.Trunc": "llvm.trunc.f64",
+}
+
+// createMathOp tries to lower the given call as a LLVM math intrinsic, if
+// possible. It returns the call result if possible, and a boolean whether it
+// succeeded. If it doesn't succeed, the architecture doesn't support the given
+// intrinsic.
+func (b *builder) createMathOp(call *ssa.CallCommon) (llvm.Value, bool) {
+	// Check whether this intrinsic is supported on the given GOARCH.
+	// If it is unsupported, this can have two reasons:
+	//
+	//  1. LLVM can expand the intrinsic inline (using float instructions), but
+	//     the result doesn't pass the tests of the math package.
+	//  2. LLVM cannot expand the intrinsic inline, will therefore lower it as a
+	//     libm function call, but the libm function call also fails the math
+	//     package tests.
+	//
+	// Whatever the implementation, it must pass the tests in the math package
+	// so unfortunately only the below intrinsic+architecture combinations are
+	// supported.
+	name := call.StaticCallee().RelString(nil)
+	switch name {
+	case "math.Ceil", "math.Floor", "math.Trunc":
+		if b.GOARCH != "wasm" && b.GOARCH != "arm64" {
+			return llvm.Value{}, false
+		}
+	case "math.Sqrt":
+		if b.GOARCH != "wasm" && b.GOARCH != "amd64" && b.GOARCH != "386" {
+			return llvm.Value{}, false
+		}
+	default:
+		return llvm.Value{}, false // only the above functions are supported.
+	}
+
+	llvmFn := b.mod.NamedFunction(mathToLLVMMapping[name])
+	if llvmFn.IsNil() {
+		// The intrinsic doesn't exist yet, so declare it.
+		// At the moment, all supported intrinsics have the form "double
+		// foo(double %x)" so we can hardcode the signature here.
+		llvmType := llvm.FunctionType(b.ctx.DoubleType(), []llvm.Type{b.ctx.DoubleType()}, false)
+		llvmFn = llvm.AddFunction(b.mod, mathToLLVMMapping[name], llvmType)
+	}
+	// Create a call to the intrinsic.
+	args := make([]llvm.Value, len(call.Args))
+	for i, arg := range call.Args {
+		args[i] = b.getValue(arg)
+	}
+	return b.CreateCall(llvmFn, args, ""), true
+}

compiler/testdata/intrinsics-cortex-m-qemu.ll

@@ -0,0 +1,27 @@
+; ModuleID = 'intrinsics.go'
+source_filename = "intrinsics.go"
+target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv7m-none-eabi"
+
+declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)
+
+define hidden void @main.init(i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  ret void
+}
+
+define hidden double @main.mySqrt(double %x, i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  %0 = call double @math.Sqrt(double %x, i8* undef, i8* undef)
+  ret double %0
+}
+
+declare double @math.Sqrt(double, i8*, i8*)
+
+define hidden double @main.myTrunc(double %x, i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  %0 = call double @math.Trunc(double %x, i8* undef, i8* undef)
+  ret double %0
+}
+
+declare double @math.Trunc(double, i8*, i8*)

compiler/testdata/intrinsics-wasm.ll

@@ -0,0 +1,31 @@
+; ModuleID = 'intrinsics.go'
+source_filename = "intrinsics.go"
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32--wasi"
+
+declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)
+
+define hidden void @main.init(i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  ret void
+}
+
+define hidden double @main.mySqrt(double %x, i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  %0 = call double @llvm.sqrt.f64(double %x)
+  ret double %0
+}
+
+; Function Attrs: nounwind readnone speculatable willreturn
+declare double @llvm.sqrt.f64(double) #0
+
+define hidden double @main.myTrunc(double %x, i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  %0 = call double @llvm.trunc.f64(double %x)
+  ret double %0
+}
+
+; Function Attrs: nounwind readnone speculatable willreturn
+declare double @llvm.trunc.f64(double) #0
+
+attributes #0 = { nounwind readnone speculatable willreturn }

compiler/testdata/intrinsics.go

@@ -0,0 +1,14 @@
+package main
+
+// Test how intrinsics are lowered: either as regular calls to the math
+// functions or as LLVM builtins (such as llvm.sqrt.f64).
+
+import "math"
+
+func mySqrt(x float64) float64 {
+	return math.Sqrt(x)
+}
+
+func myTrunc(x float64) float64 {
+	return math.Trunc(x)
+}

src/runtime/math.go

@@ -56,15 +56,7 @@ func math_Cbrt(x float64) float64 { return math_cbrt(x) }
 func math_cbrt(x float64) float64
 
 //go:linkname math_Ceil math.Ceil
-func math_Ceil(x float64) float64 {
-	if GOARCH == "arm64" || GOARCH == "wasm" {
-		return llvm_ceil(x)
-	}
-	return math_ceil(x)
-}
-
-//export llvm.ceil.f64
-func llvm_ceil(x float64) float64
+func math_Ceil(x float64) float64 { return math_ceil(x) }
 
 //go:linkname math_ceil math.ceil
 func math_ceil(x float64) float64
@@ -112,15 +104,7 @@ func math_Exp2(x float64) float64 { return math_exp2(x) }
 func math_exp2(x float64) float64
 
 //go:linkname math_Floor math.Floor
-func math_Floor(x float64) float64 {
-	if GOARCH == "arm64" || GOARCH == "wasm" {
-		return llvm_floor(x)
-	}
-	return math_floor(x)
-}
-
-//export llvm.floor.f64
-func llvm_floor(x float64) float64
+func math_Floor(x float64) float64 { return math_floor(x) }
 
 //go:linkname math_floor math.floor
 func math_floor(x float64) float64
@@ -216,15 +200,7 @@ func math_Sinh(x float64) float64 { return math_sinh(x) }
 func math_sinh(x float64) float64
 
 //go:linkname math_Sqrt math.Sqrt
-func math_Sqrt(x float64) float64 {
-	if GOARCH == "386" || GOARCH == "amd64" || GOARCH == "wasm" {
-		return llvm_sqrt(x)
-	}
-	return math_sqrt(x)
-}
-
-//export llvm.sqrt.f64
-func llvm_sqrt(x float64) float64
+func math_Sqrt(x float64) float64 { return math_sqrt(x) }
 
 //go:linkname math_sqrt math.sqrt
 func math_sqrt(x float64) float64
@@ -242,15 +218,7 @@ func math_Tanh(x float64) float64 { return math_tanh(x) }
 func math_tanh(x float64) float64
 
 //go:linkname math_Trunc math.Trunc
-func math_Trunc(x float64) float64 {
-	if GOARCH == "arm64" || GOARCH == "wasm" {
-		return llvm_trunc(x)
-	}
-	return math_trunc(x)
-}
-
-//export llvm.trunc.f64
-func llvm_trunc(x float64) float64
+func math_Trunc(x float64) float64 { return math_trunc(x) }
 
 //go:linkname math_trunc math.trunc
 func math_trunc(x float64) float64