Rollup merge of #73724 - CryZe:wasm-saturating-casts, r=alexcrichton

Use WASM's saturating casts if they are available

WebAssembly supports saturating floating point to integer casts behind a target feature. The feature is already available on many browsers. Beginning with 1.45 Rust will start defining the behavior of floating point to integer casts to be saturating as well. For this Rust constructs additional checks on top of the `fptoui` / `fptosi` instructions it emits. Here we introduce the possibility for the codegen backend to construct saturating casts itself and only fall back to constructing the checks ourselves if that is not possible.

Resolves part of #73591

2 files changed, 331 insertions, 0 deletions

diff --git a/src/test/codegen/wasm_casts_nontrapping.rs b/src/test/codegen/wasm_casts_nontrapping.rs
new file mode 100644
index 00000000000..bd6073d8c20
--- /dev/null
+++ b/src/test/codegen/wasm_casts_nontrapping.rs
@@ -0,0 +1,162 @@
+// only-wasm32
+// compile-flags: -C target-feature=+nontrapping-fptoint
+#![crate_type = "lib"]
+
+// CHECK-LABEL: @cast_f64_i64
+#[no_mangle]
+pub fn cast_f64_i64(a: f64) -> i64 {
+    // CHECK: tail call i64 @llvm.wasm.trunc.saturate.signed.i64.f64(double {{.*}})
+    // CHECK-NEXT: ret i64 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f64_i32
+#[no_mangle]
+pub fn cast_f64_i32(a: f64) -> i32 {
+    // CHECK: tail call i32 @llvm.wasm.trunc.saturate.signed.i32.f64(double {{.*}})
+    // CHECK-NEXT: ret i32 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f32_i64
+#[no_mangle]
+pub fn cast_f32_i64(a: f32) -> i64 {
+    // CHECK: tail call i64 @llvm.wasm.trunc.saturate.signed.i64.f32(float {{.*}})
+    // CHECK-NEXT: ret i64 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f32_i32
+#[no_mangle]
+pub fn cast_f32_i32(a: f32) -> i32 {
+    // CHECK: tail call i32 @llvm.wasm.trunc.saturate.signed.i32.f32(float {{.*}})
+    // CHECK-NEXT: ret i32 {{.*}}
+    a as _
+}
+
+
+// CHECK-LABEL: @cast_f64_u64
+#[no_mangle]
+pub fn cast_f64_u64(a: f64) -> u64 {
+    // CHECK: tail call i64 @llvm.wasm.trunc.saturate.unsigned.i64.f64(double {{.*}})
+    // CHECK-NEXT: ret i64 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f64_u32
+#[no_mangle]
+pub fn cast_f64_u32(a: f64) -> u32 {
+    // CHECK: tail call i32 @llvm.wasm.trunc.saturate.unsigned.i32.f64(double {{.*}})
+    // CHECK-NEXT: ret i32 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f32_u64
+#[no_mangle]
+pub fn cast_f32_u64(a: f32) -> u64 {
+    // CHECK: tail call i64 @llvm.wasm.trunc.saturate.unsigned.i64.f32(float {{.*}})
+    // CHECK-NEXT: ret i64 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f32_u32
+#[no_mangle]
+pub fn cast_f32_u32(a: f32) -> u32 {
+    // CHECK: tail call i32 @llvm.wasm.trunc.saturate.unsigned.i32.f32(float {{.*}})
+    // CHECK-NEXT: ret i32 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f32_u8
+#[no_mangle]
+pub fn cast_f32_u8(a: f32) -> u8 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui float {{.*}} to i8
+    // CHECK-NEXT: select i1 {{.*}}, i8 {{.*}}, i8 {{.*}}
+    // CHECK-NEXT: ret i8 {{.*}}
+    a as _
+}
+
+
+
+// CHECK-LABEL: @cast_unchecked_f64_i64
+#[no_mangle]
+pub unsafe fn cast_unchecked_f64_i64(a: f64) -> i64 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptosi double {{.*}} to i64
+    // CHECK-NEXT: ret i64 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f64_i32
+#[no_mangle]
+pub unsafe fn cast_unchecked_f64_i32(a: f64) -> i32 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptosi double {{.*}} to i32
+    // CHECK-NEXT: ret i32 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f32_i64
+#[no_mangle]
+pub unsafe fn cast_unchecked_f32_i64(a: f32) -> i64 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptosi float {{.*}} to i64
+    // CHECK-NEXT: ret i64 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f32_i32
+#[no_mangle]
+pub unsafe fn cast_unchecked_f32_i32(a: f32) -> i32 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptosi float {{.*}} to i32
+    // CHECK-NEXT: ret i32 {{.*}}
+    a.to_int_unchecked()
+}
+
+
+// CHECK-LABEL: @cast_unchecked_f64_u64
+#[no_mangle]
+pub unsafe fn cast_unchecked_f64_u64(a: f64) -> u64 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui double {{.*}} to i64
+    // CHECK-NEXT: ret i64 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f64_u32
+#[no_mangle]
+pub unsafe fn cast_unchecked_f64_u32(a: f64) -> u32 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui double {{.*}} to i32
+    // CHECK-NEXT: ret i32 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f32_u64
+#[no_mangle]
+pub unsafe fn cast_unchecked_f32_u64(a: f32) -> u64 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui float {{.*}} to i64
+    // CHECK-NEXT: ret i64 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f32_u32
+#[no_mangle]
+pub unsafe fn cast_unchecked_f32_u32(a: f32) -> u32 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui float {{.*}} to i32
+    // CHECK-NEXT: ret i32 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f32_u8
+#[no_mangle]
+pub unsafe fn cast_unchecked_f32_u8(a: f32) -> u8 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui float {{.*}} to i8
+    // CHECK-NEXT: ret i8 {{.*}}
+    a.to_int_unchecked()
+}
diff --git a/src/test/codegen/wasm_casts_trapping.rs b/src/test/codegen/wasm_casts_trapping.rs
new file mode 100644
index 00000000000..45b90519049
--- /dev/null
+++ b/src/test/codegen/wasm_casts_trapping.rs
@@ -0,0 +1,169 @@
+// only-wasm32
+// compile-flags: -C target-feature=-nontrapping-fptoint
+#![crate_type = "lib"]
+
+// CHECK-LABEL: @cast_f64_i64
+#[no_mangle]
+pub fn cast_f64_i64(a: f64) -> i64 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptosi double {{.*}} to i64
+    // CHECK-NEXT: select i1 {{.*}}, i64 {{.*}}, i64 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f64_i32
+#[no_mangle]
+pub fn cast_f64_i32(a: f64) -> i32 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptosi double {{.*}} to i32
+    // CHECK-NEXT: select i1 {{.*}}, i32 {{.*}}, i32 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f32_i64
+#[no_mangle]
+pub fn cast_f32_i64(a: f32) -> i64 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptosi float {{.*}} to i64
+    // CHECK-NEXT: select i1 {{.*}}, i64 {{.*}}, i64 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f32_i32
+#[no_mangle]
+pub fn cast_f32_i32(a: f32) -> i32 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptosi float {{.*}} to i32
+    // CHECK-NEXT: select i1 {{.*}}, i32 {{.*}}, i32 {{.*}}
+    a as _
+}
+
+
+// CHECK-LABEL: @cast_f64_u64
+#[no_mangle]
+pub fn cast_f64_u64(a: f64) -> u64 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui double {{.*}} to i64
+    // CHECK-NEXT: select i1 {{.*}}, i64 {{.*}}, i64 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f64_u32
+#[no_mangle]
+pub fn cast_f64_u32(a: f64) -> u32 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui double {{.*}} to i32
+    // CHECK-NEXT: select i1 {{.*}}, i32 {{.*}}, i32 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f32_u64
+#[no_mangle]
+pub fn cast_f32_u64(a: f32) -> u64 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui float {{.*}} to i64
+    // CHECK-NEXT: select i1 {{.*}}, i64 {{.*}}, i64 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f32_u32
+#[no_mangle]
+pub fn cast_f32_u32(a: f32) -> u32 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui float {{.*}} to i32
+    // CHECK-NEXT: select i1 {{.*}}, i32 {{.*}}, i32 {{.*}}
+    a as _
+}
+
+// CHECK-LABEL: @cast_f32_u8
+#[no_mangle]
+pub fn cast_f32_u8(a: f32) -> u8 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui float {{.*}} to i8
+    // CHECK-NEXT: select i1 {{.*}}, i8 {{.*}}, i8 {{.*}}
+    a as _
+}
+
+
+
+// CHECK-LABEL: @cast_unchecked_f64_i64
+#[no_mangle]
+pub unsafe fn cast_unchecked_f64_i64(a: f64) -> i64 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptosi double {{.*}} to i64
+    // CHECK-NEXT: ret i64 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f64_i32
+#[no_mangle]
+pub unsafe fn cast_unchecked_f64_i32(a: f64) -> i32 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptosi double {{.*}} to i32
+    // CHECK-NEXT: ret i32 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f32_i64
+#[no_mangle]
+pub unsafe fn cast_unchecked_f32_i64(a: f32) -> i64 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptosi float {{.*}} to i64
+    // CHECK-NEXT: ret i64 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f32_i32
+#[no_mangle]
+pub unsafe fn cast_unchecked_f32_i32(a: f32) -> i32 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptosi float {{.*}} to i32
+    // CHECK-NEXT: ret i32 {{.*}}
+    a.to_int_unchecked()
+}
+
+
+// CHECK-LABEL: @cast_unchecked_f64_u64
+#[no_mangle]
+pub unsafe fn cast_unchecked_f64_u64(a: f64) -> u64 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui double {{.*}} to i64
+    // CHECK-NEXT: ret i64 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f64_u32
+#[no_mangle]
+pub unsafe fn cast_unchecked_f64_u32(a: f64) -> u32 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui double {{.*}} to i32
+    // CHECK-NEXT: ret i32 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f32_u64
+#[no_mangle]
+pub unsafe fn cast_unchecked_f32_u64(a: f32) -> u64 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui float {{.*}} to i64
+    // CHECK-NEXT: ret i64 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f32_u32
+#[no_mangle]
+pub unsafe fn cast_unchecked_f32_u32(a: f32) -> u32 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui float {{.*}} to i32
+    // CHECK-NEXT: ret i32 {{.*}}
+    a.to_int_unchecked()
+}
+
+// CHECK-LABEL: @cast_unchecked_f32_u8
+#[no_mangle]
+pub unsafe fn cast_unchecked_f32_u8(a: f32) -> u8 {
+    // CHECK-NOT: {{.*}} call {{.*}} @llvm.wasm.trunc.{{.*}}
+    // CHECK: fptoui float {{.*}} to i8
+    // CHECK-NEXT: ret i8 {{.*}}
+    a.to_int_unchecked()
+}