From 21718dc59b1c0fb326b1e0e828150435207c5fa6 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Fri, 31 Jul 2026 15:48:52 -0700
Subject: [PATCH] compiler: fix 64-bit sin and cos on AVR

---
 compiler/intrinsics.go | 11 +++++++++++
 main_test.go           |  8 ++++----
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/compiler/intrinsics.go b/compiler/intrinsics.go
index 9df0bda3b..a31359a33 100644
--- a/compiler/intrinsics.go
+++ b/compiler/intrinsics.go
@@ -201,6 +201,17 @@ func (b *builder) defineMathOp() bool {
 	if !ok {
 		return false
 	}
+	if strings.HasPrefix(b.Triple, "avr") {
+		// LLVM assumes the traditional AVR ABI where double is 32 bits and
+		// therefore does not provide f64 runtime libcalls for sin and cos.
+		// TinyGo uses 64-bit doubles on AVR, which picolibc supports directly.
+		switch b.fn.Name() {
+		case "Cos":
+			llvmName = "cos"
+		case "Sin":
+			llvmName = "sin"
+		}
+	}
 	if strings.HasSuffix(b.Triple, "-wasi") || llvmutil.Version() < 19 {
 		// We don't have a real libc for wasip2. Until that is fixed, we need to
 		// limit math intrinsics on WASI to a subset supported natively in
diff --git a/main_test.go b/main_test.go
index c32ceacd1..07c531a39 100644
--- a/main_test.go
+++ b/main_test.go
@@ -370,10 +370,6 @@ func runPlatTests(options compileopts.Options, tests []string, t *testing.T) {
 				// Too big for AVR. Doesn't fit in flash/RAM.
 				continue
 
-			case "math.go":
-				// LLVM fails to lower one of the required library calls.
-				continue
-
 			case "cgo/":
 				// CGo function pointers don't work on AVR (needs LLVM 16 and
 				// some compiler changes).
@@ -432,6 +428,10 @@ func runPlatTests(options compileopts.Options, tests []string, t *testing.T) {
 			if name == "finalizerinvariants.go" || name == "finalizerlarge.go" {
 				testOptions.Tags = append(append([]string(nil), options.Tags...), "runtime_asserts")
 			}
+			if testOptions.Target == "simavr" && name == "math.go" {
+				// This test exceeds simavr's default 384-byte goroutine stack.
+				testOptions.StackSize = 512
+			}
 			runTest(name, testOptions, t, nil, nil)
 		})
 	}