[X86] Add some demanded bits test cases for PDEP with constant mask

The number of ones in the mask for the PDEP determines how many
bits of the other operand are used. If the mask is constant we
can use this to build a mask for SimplifyDemandedBits. This can
be used to replace the extends in the test with anyextend.

Author: topperc

llvm/test/CodeGen/X86/bmi2-x86_64.ll

@@ -41,6 +41,18 @@ define i64 @pdep64_load(i64 %x, i64* %y)   {
   ret i64 %tmp
 }
 
+define i64 @pdep64_anyext(i32 %x)   {
+; CHECK-LABEL: pdep64_anyext:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movslq %edi, %rax
+; CHECK-NEXT:    movabsq $6148914691236517205, %rcx # imm = 0x5555555555555555
+; CHECK-NEXT:    pdepq %rcx, %rax, %rax
+; CHECK-NEXT:    retq
+  %x1 = sext i32 %x to i64
+  %tmp = tail call i64 @llvm.x86.bmi.pdep.64(i64 %x1, i64 6148914691236517205)
+  ret i64 %tmp
+}
+
 declare i64 @llvm.x86.bmi.pdep.64(i64, i64)
 
 define i64 @pext64(i64 %x, i64 %y)   {

llvm/test/CodeGen/X86/bmi2.ll

@@ -76,6 +76,25 @@ define i32 @pdep32_load(i32 %x, i32* %y)   {
   ret i32 %tmp
 }
 
+define i32 @pdep32_anyext(i16 %x)   {
+; X86-LABEL: pdep32_anyext:
+; X86:       # %bb.0:
+; X86-NEXT:    movswl {{[0-9]+}}(%esp), %eax
+; X86-NEXT:    movl $-1431655766, %ecx # imm = 0xAAAAAAAA
+; X86-NEXT:    pdepl %ecx, %eax, %eax
+; X86-NEXT:    retl
+;
+; X64-LABEL: pdep32_anyext:
+; X64:       # %bb.0:
+; X64-NEXT:    movswl %di, %eax
+; X64-NEXT:    movl $-1431655766, %ecx # imm = 0xAAAAAAAA
+; X64-NEXT:    pdepl %ecx, %eax, %eax
+; X64-NEXT:    retq
+  %x1 = sext i16 %x to i32
+  %tmp = tail call i32 @llvm.x86.bmi.pdep.32(i32 %x1, i32 -1431655766)
+  ret i32 %tmp
+}
+
 declare i32 @llvm.x86.bmi.pdep.32(i32, i32)
 
 define i32 @pext32(i32 %x, i32 %y)   {