Index: llvm/lib/Target/AMDGPU/AMDGPUPostLegalizerCombiner.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/AMDGPUPostLegalizerCombiner.cpp
+++ llvm/lib/Target/AMDGPU/AMDGPUPostLegalizerCombiner.cpp
@@ -137,9 +137,11 @@
   // about in practice.
   LLT Ty = MRI.getType(DstReg);
   if (Ty == LLT::scalar(32) || Ty == LLT::scalar(16)) {
-    const APInt Mask = APInt::getHighBitsSet(32, 24);
-    return Helper.getKnownBits()->maskedValueIsZero(MI.getOperand(1).getReg(),
-                                                    Mask);
+    Register SrcReg = MI.getOperand(1).getReg();
+    unsigned SrcSize = MRI.getType(SrcReg).getSizeInBits();
+    assert(SrcSize == 16 || SrcSize == 32 || SrcSize == 64);
+    const APInt Mask = APInt::getHighBitsSet(SrcSize, SrcSize - 8);
+    return Helper.getKnownBits()->maskedValueIsZero(SrcReg, Mask);
   }
 
   return false;
@@ -151,14 +153,18 @@
   const LLT S32 = LLT::scalar(32);
 
   Register DstReg = MI.getOperand(0).getReg();
+  Register SrcReg = MI.getOperand(1).getReg();
   LLT Ty = B.getMRI()->getType(DstReg);
+  LLT SrcTy = B.getMRI()->getType(SrcReg);
+  if (SrcTy != S32)
+    SrcReg = B.buildAnyExtOrTrunc(S32,SrcReg).getReg(0);
 
   if (Ty == S32) {
     B.buildInstr(AMDGPU::G_AMDGPU_CVT_F32_UBYTE0, {DstReg},
-                   {MI.getOperand(1)}, MI.getFlags());
+                   {SrcReg}, MI.getFlags());
   } else {
     auto Cvt0 = B.buildInstr(AMDGPU::G_AMDGPU_CVT_F32_UBYTE0, {S32},
-                             {MI.getOperand(1)}, MI.getFlags());
+                             {SrcReg}, MI.getFlags());
     B.buildFPTrunc(DstReg, Cvt0, MI.getFlags());
   }
 
Index: llvm/test/CodeGen/AMDGPU/GlobalISel/combine-itofp.mir
===================================================================
--- llvm/test/CodeGen/AMDGPU/GlobalISel/combine-itofp.mir
+++ llvm/test/CodeGen/AMDGPU/GlobalISel/combine-itofp.mir
@@ -173,3 +173,95 @@
     %4:_(s32) = G_ANYEXT %3
     $vgpr0 = COPY %4
 ...
+
+---
+name: uitofp_s64_char_to_f32
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $vgpr0_vgpr1
+
+    ; CHECK-LABEL: name: uitofp_s64_char_to_f32
+    ; CHECK: liveins: $vgpr0_vgpr1
+    ; CHECK: [[COPY:%[0-9]+]]:_(s64) = COPY $vgpr0_vgpr1
+    ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 255
+    ; CHECK: [[AND:%[0-9]+]]:_(s64) = G_AND [[COPY]], [[C]]
+    ; CHECK: [[TRUNC:%[0-9]+]]:_(s32) = G_TRUNC [[AND]](s64)
+    ; CHECK: [[AMDGPU_CVT_F32_UBYTE0_:%[0-9]+]]:_(s32) = G_AMDGPU_CVT_F32_UBYTE0 [[TRUNC]]
+    ; CHECK: $vgpr0 = COPY [[AMDGPU_CVT_F32_UBYTE0_]](s32)
+    %0:_(s64) = COPY $vgpr0_vgpr1
+    %1:_(s64) = G_CONSTANT i64 255
+    %2:_(s64) = G_AND %0, %1
+    %3:_(s32) = G_UITOFP %2
+    $vgpr0 = COPY %3
+...
+
+---
+name: sitofp_s64_char_to_f32
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $vgpr0_vgpr1
+
+    ; CHECK-LABEL: name: sitofp_s64_char_to_f32
+    ; CHECK: liveins: $vgpr0_vgpr1
+    ; CHECK: [[COPY:%[0-9]+]]:_(s64) = COPY $vgpr0_vgpr1
+    ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 255
+    ; CHECK: [[AND:%[0-9]+]]:_(s64) = G_AND [[COPY]], [[C]]
+    ; CHECK: [[TRUNC:%[0-9]+]]:_(s32) = G_TRUNC [[AND]](s64)
+    ; CHECK: [[AMDGPU_CVT_F32_UBYTE0_:%[0-9]+]]:_(s32) = G_AMDGPU_CVT_F32_UBYTE0 [[TRUNC]]
+    ; CHECK: $vgpr0 = COPY [[AMDGPU_CVT_F32_UBYTE0_]](s32)
+    %0:_(s64) = COPY $vgpr0_vgpr1
+    %1:_(s64) = G_CONSTANT i64 255
+    %2:_(s64) = G_AND %0, %1
+    %3:_(s32) = G_SITOFP %2
+    $vgpr0 = COPY %3
+...
+
+---
+name: uitofp_s16_char_to_f32
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $vgpr0
+
+    ; CHECK-LABEL: name: uitofp_s16_char_to_f32
+    ; CHECK: liveins: $vgpr0
+    ; CHECK: [[COPY:%[0-9]+]]:_(s32) = COPY $vgpr0
+    ; CHECK: [[TRUNC:%[0-9]+]]:_(s16) = G_TRUNC [[COPY]](s32)
+    ; CHECK: [[C:%[0-9]+]]:_(s16) = G_CONSTANT i16 255
+    ; CHECK: [[AND:%[0-9]+]]:_(s16) = G_AND [[TRUNC]], [[C]]
+    ; CHECK: [[ANYEXT:%[0-9]+]]:_(s32) = G_ANYEXT [[AND]](s16)
+    ; CHECK: [[AMDGPU_CVT_F32_UBYTE0_:%[0-9]+]]:_(s32) = G_AMDGPU_CVT_F32_UBYTE0 [[ANYEXT]]
+    ; CHECK: $vgpr0 = COPY [[AMDGPU_CVT_F32_UBYTE0_]](s32)
+    %0:_(s32) = COPY $vgpr0
+    %1:_(s16) = G_TRUNC %0
+    %2:_(s16) = G_CONSTANT i16 255
+    %3:_(s16) = G_AND %1, %2
+    %4:_(s32) = G_UITOFP %3
+    $vgpr0 = COPY %4
+...
+
+---
+name: sitofp_s16_char_to_f32
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $vgpr0
+
+    ; CHECK-LABEL: name: sitofp_s16_char_to_f32
+    ; CHECK: liveins: $vgpr0
+    ; CHECK: [[COPY:%[0-9]+]]:_(s32) = COPY $vgpr0
+    ; CHECK: [[TRUNC:%[0-9]+]]:_(s16) = G_TRUNC [[COPY]](s32)
+    ; CHECK: [[C:%[0-9]+]]:_(s16) = G_CONSTANT i16 255
+    ; CHECK: [[AND:%[0-9]+]]:_(s16) = G_AND [[TRUNC]], [[C]]
+    ; CHECK: [[ANYEXT:%[0-9]+]]:_(s32) = G_ANYEXT [[AND]](s16)
+    ; CHECK: [[AMDGPU_CVT_F32_UBYTE0_:%[0-9]+]]:_(s32) = G_AMDGPU_CVT_F32_UBYTE0 [[ANYEXT]]
+    ; CHECK: $vgpr0 = COPY [[AMDGPU_CVT_F32_UBYTE0_]](s32)
+    %0:_(s32) = COPY $vgpr0
+    %1:_(s16) = G_TRUNC %0
+    %2:_(s16) = G_CONSTANT i16 255
+    %3:_(s16) = G_AND %1, %2
+    %4:_(s32) = G_SITOFP %3
+    $vgpr0 = COPY %4
+...
Index: llvm/test/CodeGen/AMDGPU/GlobalISel/cvt_f32_ubyte.ll
===================================================================
--- llvm/test/CodeGen/AMDGPU/GlobalISel/cvt_f32_ubyte.ll
+++ llvm/test/CodeGen/AMDGPU/GlobalISel/cvt_f32_ubyte.ll
@@ -1142,3 +1142,187 @@
   store float %add, float addrspace(1)* %out
   ret void
 }
+
+define float @v_test_sitofp_i64_byte_to_f32(i64 %arg0) {
+; SI-LABEL: v_test_sitofp_i64_byte_to_f32:
+; SI:       ; %bb.0:
+; SI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; SI-NEXT:    s_movk_i32 s6, 0xff
+; SI-NEXT:    v_and_b32_e32 v2, s6, v0
+; SI-NEXT:    v_add_i32_e32 v2, vcc, 0, v2
+; SI-NEXT:    v_ffbh_u32_e32 v4, v2
+; SI-NEXT:    v_addc_u32_e64 v3, s[4:5], 0, 0, vcc
+; SI-NEXT:    v_add_i32_e32 v4, vcc, 32, v4
+; SI-NEXT:    v_ffbh_u32_e32 v5, v3
+; SI-NEXT:    v_cmp_eq_u32_e32 vcc, 0, v3
+; SI-NEXT:    v_cndmask_b32_e32 v4, v5, v4, vcc
+; SI-NEXT:    v_mov_b32_e32 v5, 0xbe
+; SI-NEXT:    v_sub_i32_e32 v6, vcc, v5, v4
+; SI-NEXT:    v_lshl_b64 v[4:5], v[2:3], v4
+; SI-NEXT:    v_cmp_ne_u64_e32 vcc, 0, v[2:3]
+; SI-NEXT:    v_and_b32_e32 v3, 0x7fffffff, v5
+; SI-NEXT:    v_cndmask_b32_e32 v2, 0, v6, vcc
+; SI-NEXT:    v_and_b32_e32 v5, s6, v3
+; SI-NEXT:    v_lshrrev_b32_e32 v3, 8, v3
+; SI-NEXT:    v_lshlrev_b32_e32 v2, 23, v2
+; SI-NEXT:    s_mov_b32 s4, 0
+; SI-NEXT:    s_movk_i32 s5, 0x80
+; SI-NEXT:    v_or_b32_e32 v2, v2, v3
+; SI-NEXT:    v_cmp_eq_u64_e32 vcc, s[4:5], v[4:5]
+; SI-NEXT:    v_and_b32_e32 v3, 1, v2
+; SI-NEXT:    v_cndmask_b32_e32 v3, 0, v3, vcc
+; SI-NEXT:    v_cmp_lt_u64_e32 vcc, s[4:5], v[4:5]
+; SI-NEXT:    v_mov_b32_e32 v0, 0
+; SI-NEXT:    v_cndmask_b32_e64 v3, v3, 1, vcc
+; SI-NEXT:    v_mov_b32_e32 v1, v0
+; SI-NEXT:    v_add_i32_e32 v2, vcc, v2, v3
+; SI-NEXT:    v_cmp_ne_u64_e32 vcc, 0, v[0:1]
+; SI-NEXT:    v_cndmask_b32_e64 v0, v2, -v2, vcc
+; SI-NEXT:    s_setpc_b64 s[30:31]
+;
+; VI-LABEL: v_test_sitofp_i64_byte_to_f32:
+; VI:       ; %bb.0:
+; VI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; VI-NEXT:    s_movk_i32 s6, 0xff
+; VI-NEXT:    v_and_b32_e32 v2, s6, v0
+; VI-NEXT:    v_add_u32_e32 v2, vcc, 0, v2
+; VI-NEXT:    v_ffbh_u32_e32 v4, v2
+; VI-NEXT:    v_addc_u32_e64 v3, s[4:5], 0, 0, vcc
+; VI-NEXT:    v_add_u32_e32 v4, vcc, 32, v4
+; VI-NEXT:    v_ffbh_u32_e32 v5, v3
+; VI-NEXT:    v_cmp_eq_u32_e32 vcc, 0, v3
+; VI-NEXT:    v_cndmask_b32_e32 v4, v5, v4, vcc
+; VI-NEXT:    v_mov_b32_e32 v5, 0xbe
+; VI-NEXT:    v_sub_u32_e32 v6, vcc, v5, v4
+; VI-NEXT:    v_lshlrev_b64 v[4:5], v4, v[2:3]
+; VI-NEXT:    v_cmp_ne_u64_e32 vcc, 0, v[2:3]
+; VI-NEXT:    v_and_b32_e32 v3, 0x7fffffff, v5
+; VI-NEXT:    v_cndmask_b32_e32 v2, 0, v6, vcc
+; VI-NEXT:    v_and_b32_e32 v5, s6, v3
+; VI-NEXT:    v_lshrrev_b32_e32 v3, 8, v3
+; VI-NEXT:    v_lshlrev_b32_e32 v2, 23, v2
+; VI-NEXT:    s_mov_b32 s4, 0
+; VI-NEXT:    s_movk_i32 s5, 0x80
+; VI-NEXT:    v_or_b32_e32 v2, v2, v3
+; VI-NEXT:    v_cmp_eq_u64_e32 vcc, s[4:5], v[4:5]
+; VI-NEXT:    v_and_b32_e32 v3, 1, v2
+; VI-NEXT:    v_cndmask_b32_e32 v3, 0, v3, vcc
+; VI-NEXT:    v_cmp_lt_u64_e32 vcc, s[4:5], v[4:5]
+; VI-NEXT:    v_mov_b32_e32 v0, 0
+; VI-NEXT:    v_cndmask_b32_e64 v3, v3, 1, vcc
+; VI-NEXT:    v_mov_b32_e32 v1, v0
+; VI-NEXT:    v_add_u32_e32 v2, vcc, v2, v3
+; VI-NEXT:    v_cmp_ne_u64_e32 vcc, 0, v[0:1]
+; VI-NEXT:    v_cndmask_b32_e64 v0, v2, -v2, vcc
+; VI-NEXT:    s_setpc_b64 s[30:31]
+  %masked = and i64 %arg0, 255
+  %itofp = sitofp i64 %masked to float
+  ret float %itofp
+}
+
+define float @v_test_uitofp_i64_byte_to_f32(i64 %arg0) {
+; SI-LABEL: v_test_uitofp_i64_byte_to_f32:
+; SI:       ; %bb.0:
+; SI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; SI-NEXT:    s_movk_i32 s4, 0xff
+; SI-NEXT:    v_and_b32_e32 v0, s4, v0
+; SI-NEXT:    v_ffbh_u32_e32 v2, v0
+; SI-NEXT:    v_add_i32_e32 v2, vcc, 32, v2
+; SI-NEXT:    v_ffbh_u32_e32 v3, 0
+; SI-NEXT:    v_cmp_eq_u32_e64 vcc, 0, 0
+; SI-NEXT:    v_cndmask_b32_e32 v2, v3, v2, vcc
+; SI-NEXT:    v_mov_b32_e32 v3, 0xbe
+; SI-NEXT:    v_mov_b32_e32 v1, 0
+; SI-NEXT:    v_sub_i32_e32 v4, vcc, v3, v2
+; SI-NEXT:    v_lshl_b64 v[2:3], v[0:1], v2
+; SI-NEXT:    v_cmp_ne_u64_e32 vcc, 0, v[0:1]
+; SI-NEXT:    v_and_b32_e32 v1, 0x7fffffff, v3
+; SI-NEXT:    v_cndmask_b32_e32 v0, 0, v4, vcc
+; SI-NEXT:    v_and_b32_e32 v3, s4, v1
+; SI-NEXT:    v_lshrrev_b32_e32 v1, 8, v1
+; SI-NEXT:    v_lshlrev_b32_e32 v0, 23, v0
+; SI-NEXT:    s_mov_b32 s4, 0
+; SI-NEXT:    s_movk_i32 s5, 0x80
+; SI-NEXT:    v_or_b32_e32 v0, v0, v1
+; SI-NEXT:    v_cmp_eq_u64_e32 vcc, s[4:5], v[2:3]
+; SI-NEXT:    v_and_b32_e32 v1, 1, v0
+; SI-NEXT:    v_cndmask_b32_e32 v1, 0, v1, vcc
+; SI-NEXT:    v_cmp_lt_u64_e32 vcc, s[4:5], v[2:3]
+; SI-NEXT:    v_cndmask_b32_e64 v1, v1, 1, vcc
+; SI-NEXT:    v_add_i32_e32 v0, vcc, v0, v1
+; SI-NEXT:    s_setpc_b64 s[30:31]
+;
+; VI-LABEL: v_test_uitofp_i64_byte_to_f32:
+; VI:       ; %bb.0:
+; VI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; VI-NEXT:    s_movk_i32 s4, 0xff
+; VI-NEXT:    v_and_b32_e32 v0, s4, v0
+; VI-NEXT:    v_ffbh_u32_e32 v2, v0
+; VI-NEXT:    v_add_u32_e32 v2, vcc, 32, v2
+; VI-NEXT:    v_ffbh_u32_e32 v3, 0
+; VI-NEXT:    v_cmp_eq_u32_e64 vcc, 0, 0
+; VI-NEXT:    v_cndmask_b32_e32 v2, v3, v2, vcc
+; VI-NEXT:    v_mov_b32_e32 v3, 0xbe
+; VI-NEXT:    v_mov_b32_e32 v1, 0
+; VI-NEXT:    v_sub_u32_e32 v4, vcc, v3, v2
+; VI-NEXT:    v_lshlrev_b64 v[2:3], v2, v[0:1]
+; VI-NEXT:    v_cmp_ne_u64_e32 vcc, 0, v[0:1]
+; VI-NEXT:    v_and_b32_e32 v1, 0x7fffffff, v3
+; VI-NEXT:    v_cndmask_b32_e32 v0, 0, v4, vcc
+; VI-NEXT:    v_and_b32_e32 v3, s4, v1
+; VI-NEXT:    v_lshrrev_b32_e32 v1, 8, v1
+; VI-NEXT:    v_lshlrev_b32_e32 v0, 23, v0
+; VI-NEXT:    s_mov_b32 s4, 0
+; VI-NEXT:    s_movk_i32 s5, 0x80
+; VI-NEXT:    v_or_b32_e32 v0, v0, v1
+; VI-NEXT:    v_cmp_eq_u64_e32 vcc, s[4:5], v[2:3]
+; VI-NEXT:    v_and_b32_e32 v1, 1, v0
+; VI-NEXT:    v_cndmask_b32_e32 v1, 0, v1, vcc
+; VI-NEXT:    v_cmp_lt_u64_e32 vcc, s[4:5], v[2:3]
+; VI-NEXT:    v_cndmask_b32_e64 v1, v1, 1, vcc
+; VI-NEXT:    v_add_u32_e32 v0, vcc, v0, v1
+; VI-NEXT:    s_setpc_b64 s[30:31]
+  %masked = and i64 %arg0, 255
+  %itofp = uitofp i64 %masked to float
+  ret float %itofp
+}
+
+define float @v_test_sitofp_i16_byte_to_f32(i16 %arg0) {
+; SI-LABEL: v_test_sitofp_i16_byte_to_f32:
+; SI:       ; %bb.0:
+; SI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; SI-NEXT:    v_and_b32_e32 v0, 0xff, v0
+; SI-NEXT:    v_bfe_i32 v0, v0, 0, 16
+; SI-NEXT:    v_cvt_f32_ubyte0_e32 v0, v0
+; SI-NEXT:    s_setpc_b64 s[30:31]
+;
+; VI-LABEL: v_test_sitofp_i16_byte_to_f32:
+; VI:       ; %bb.0:
+; VI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; VI-NEXT:    v_and_b32_e32 v0, 0xff, v0
+; VI-NEXT:    v_cvt_f32_ubyte0_sdwa v0, sext(v0) dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_0
+; VI-NEXT:    s_setpc_b64 s[30:31]
+  %masked = and i16 %arg0, 255
+  %itofp = sitofp i16 %masked to float
+  ret float %itofp
+}
+
+define float @v_test_uitofp_i16_byte_to_f32(i16 %arg0) {
+; SI-LABEL: v_test_uitofp_i16_byte_to_f32:
+; SI:       ; %bb.0:
+; SI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; SI-NEXT:    v_and_b32_e32 v0, 0xff, v0
+; SI-NEXT:    v_bfe_u32 v0, v0, 0, 16
+; SI-NEXT:    v_cvt_f32_ubyte0_e32 v0, v0
+; SI-NEXT:    s_setpc_b64 s[30:31]
+;
+; VI-LABEL: v_test_uitofp_i16_byte_to_f32:
+; VI:       ; %bb.0:
+; VI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; VI-NEXT:    v_and_b32_e32 v0, 0xff, v0
+; VI-NEXT:    v_cvt_f32_ubyte0_sdwa v0, v0 dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_0
+; VI-NEXT:    s_setpc_b64 s[30:31]
+  %masked = and i16 %arg0, 255
+  %itofp = uitofp i16 %masked to float
+  ret float %itofp
+}