Specify the integer type of the powi LLVM intrinsic

Since LLVM <https://reviews.llvm.org/D99439> (4c7f820, "Update
@llvm.powi to handle different int sizes for the exponent"), the size of
the integer can be specified for the `powi` intrinsic. Make use of this
so it is more obvious that integer size is consistent across all float
types.

This feature is available since LLVM 13 (October 2021). Based on
bootstrap we currently support >= 17.0, so there should be no support
problems.

compiler/rustc_codegen_llvm/src/context.rs

@@ -775,10 +775,10 @@ impl<'ll> CodegenCx<'ll, '_> {
         ifn!("llvm.debugtrap", fn() -> void);
         ifn!("llvm.frameaddress", fn(t_i32) -> ptr);
 
-        ifn!("llvm.powi.f16", fn(t_f16, t_i32) -> t_f16);
-        ifn!("llvm.powi.f32", fn(t_f32, t_i32) -> t_f32);
-        ifn!("llvm.powi.f64", fn(t_f64, t_i32) -> t_f64);
-        ifn!("llvm.powi.f128", fn(t_f128, t_i32) -> t_f128);
+        ifn!("llvm.powi.f16.i32", fn(t_f16, t_i32) -> t_f16);
+        ifn!("llvm.powi.f32.i32", fn(t_f32, t_i32) -> t_f32);
+        ifn!("llvm.powi.f64.i32", fn(t_f64, t_i32) -> t_f64);
+        ifn!("llvm.powi.f128.i32", fn(t_f128, t_i32) -> t_f128);
 
         ifn!("llvm.pow.f16", fn(t_f16, t_f16) -> t_f16);
         ifn!("llvm.pow.f32", fn(t_f32, t_f32) -> t_f32);

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -35,10 +35,10 @@ fn get_simple_intrinsic<'ll>(
         sym::sqrtf64 => "llvm.sqrt.f64",
         sym::sqrtf128 => "llvm.sqrt.f128",
 
-        sym::powif16 => "llvm.powi.f16",
-        sym::powif32 => "llvm.powi.f32",
-        sym::powif64 => "llvm.powi.f64",
-        sym::powif128 => "llvm.powi.f128",
+        sym::powif16 => "llvm.powi.f16.i32",
+        sym::powif32 => "llvm.powi.f32.i32",
+        sym::powif64 => "llvm.powi.f64.i32",
+        sym::powif128 => "llvm.powi.f128.i32",
 
         sym::sinf16 => "llvm.sin.f16",
         sym::sinf32 => "llvm.sin.f32",