Use fmul in log10 intrinsic

Fixes #199.

Author: LegNeato

CHANGELOG.md

@@ -48,6 +48,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed 🩹
 
+- [PR#200](https://github.com/Rust-GPU/rust-gpu/pull/200) fixed [#199](https://github.com/Rust-GPU/rust-gpu/issues/199) by correctly generating an `fmul` in the `log10` intrinsic
 - [PR#174](https://github.com/Rust-GPU/rust-gpu/pull/174) fixed [#169](https://github.com/Rust-GPU/rust-gpu/issues/169) by handling signed integers in the `bswap` intrinsic
 - [PR#1129](https://github.com/EmbarkStudios/rust-gpu/pull/1129) fixed [#1062](https://github.com/EmbarkStudios/rust-gpu/issues/1062) by not flipping the comparison of the rotate amount with zero
 

crates/rustc_codegen_spirv/src/builder/intrinsics.rs

@@ -174,7 +174,7 @@ impl<'a, 'tcx> IntrinsicCallBuilderMethods<'tcx> for Builder<'a, 'tcx> {
                 // log10(x) == (1 / ln(10)) * ln(x)
                 let mul = self.constant_float(args[0].immediate().ty, 1.0 / 10.0f64.ln());
                 let ln = self.gl_op(GLOp::Log, ret_ty, [args[0].immediate()]);
-                self.mul(mul, ln)
+                self.fmul(mul, ln)
             }
             sym::fmaf32 | sym::fmaf64 => self.gl_op(GLOp::Fma, ret_ty, [
                 args[0].immediate(),

crates/rustc_codegen_spirv/src/builder/libm_intrinsics.rs

@@ -240,7 +240,7 @@ impl Builder<'_, '_> {
                 // log10(x) == (1 / ln(10)) * ln(x)
                 let mul = self.constant_float(args[0].ty, 1.0 / 10.0f64.ln());
                 let ln = self.gl_op(GLOp::Log, result_type, [args[0]]);
-                self.mul(mul, ln)
+                self.fmul(mul, ln)
             }
             LibmIntrinsic::Custom(LibmCustomIntrinsic::Log1p) => {
                 assert_eq!(args.len(), 1);

tests/ui/lang/core/intrinsics/log10.rs

@@ -0,0 +1,17 @@
+// Test log10 intrinsic
+// build-pass
+
+#![allow(internal_features)]
+#![feature(core_intrinsics)]
+#![no_std]
+
+use spirv_std::num_traits::Float as _;
+use spirv_std::spirv;
+
+#[spirv(compute(threads(1)))]
+pub fn main(
+    #[spirv(storage_buffer, descriptor_set = 0, binding = 0)] input: &[f32],
+    #[spirv(storage_buffer, descriptor_set = 0, binding = 1)] output: &mut [f32],
+) {
+    output[0] = input[0].log10();
+}