[clang] [llvm] [AMDGPU] Use `bf16` instead of `i16` for bfloat (PR #80908)

[Shilei Tian via cfe-commits]

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@@ -0,0 +1,8 @@
+// RUN: llvm-mc -arch=amdgcn -mcpu=gfx1100 -show-encoding %s | FileCheck %s
+// RUN: llvm-mc -arch=amdgcn -mcpu=gfx1200 -show-encoding %s | FileCheck %s
+
+v_dot2_bf16_bf16 v5, v1, v2, 100.0
+// CHECK: v_dot2_bf16_bf16 v5, v1, v2, 0x42c8 ; encoding: [0x05,0x00,0x67,0xd6,0x01,0x05,0xfe,0x03,0xc8,0x42,0x00,0x00]
+
+v_dot2_bf16_bf16 v5, v1, v2, 1.0
+// CHECK: v_dot2_bf16_bf16 v5, v1, v2, 1.0 ; encoding: [0x05,0x00,0x67,0xd6,0x01,0x05,0xca,0x03]
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shiltian wrote:

It looks like our assembler doesn't like the case such as `v_dot2_bf16_bf16 v5, v1, 0x42c842c8, 0x42c8`, even w/o this patch. Even the asm (`v_dot2_bf16_bf16 v2, s0, 0x3f803f80, v2`) generated in another file above (`llvm/test/CodeGen/AMDGPU/llvm.amdgcn.fdot2.bf16.bf16.ll`) can't be recognized by our assembler. 😄

https://github.com/llvm/llvm-project/pull/80908