[llvm] r322523 - [x86] add tests to show missed constant shrinking (PR35907); NFC

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Mon Jan 15 13:57:41 2018
New Revision: 322523

URL: http://llvm.org/viewvc/llvm-project?rev=322523&view=rev
Log:
[x86] add tests to show missed constant shrinking (PR35907); NFC

Modified:
    llvm/trunk/test/CodeGen/X86/and-encoding.ll

Modified: llvm/trunk/test/CodeGen/X86/and-encoding.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/and-encoding.ll?rev=322523&r1=322522&r2=322523&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/and-encoding.ll (original)
+++ llvm/trunk/test/CodeGen/X86/and-encoding.ll Mon Jan 15 13:57:41 2018
@@ -1,14 +1,11 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc -mtriple=x86_64-unknown-unknown -show-mc-encoding < %s | FileCheck %s
 
-; Test that the direct object emission selects the and variant with 8 bit
+; Test that the direct object emission selects the 'and' variant with 8-bit
 ; immediate.
 ; We used to get this wrong when using direct object emission, but not when
 ; reading assembly.
 
-
-target triple = "x86_64-pc-linux"
-
 define void @f1() nounwind {
 ; CHECK-LABEL: f1:
 ; CHECK:       # %bb.0:
@@ -44,3 +41,83 @@ define void @f3(i32 %x, i1 *%y) nounwind
   ret void
 }
 
+; The immediate (0x0ffffff0) can be made into an i8 by making it negative.
+
+define i32 @lopped32_32to8(i32 %x) {
+; CHECK-LABEL: lopped32_32to8:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    shrl $4, %edi # encoding: [0xc1,0xef,0x04]
+; CHECK-NEXT:    andl $268435440, %edi # encoding: [0x81,0xe7,0xf0,0xff,0xff,0x0f]
+; CHECK-NEXT:    # imm = 0xFFFFFF0
+; CHECK-NEXT:    movl %edi, %eax # encoding: [0x89,0xf8]
+; CHECK-NEXT:    retq # encoding: [0xc3]
+  %shr = lshr i32 %x, 4
+  %and = and i32 %shr, 268435440
+  ret i32 %and
+}
+
+; The immediate (0x0ffffff0) can be made into an i8 by making it negative.
+
+define i64 @lopped64_32to8(i64 %x) {
+; CHECK-LABEL: lopped64_32to8:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    shrq $36, %rdi # encoding: [0x48,0xc1,0xef,0x24]
+; CHECK-NEXT:    andl $268435440, %edi # encoding: [0x81,0xe7,0xf0,0xff,0xff,0x0f]
+; CHECK-NEXT:    # imm = 0xFFFFFF0
+; CHECK-NEXT:    movq %rdi, %rax # encoding: [0x48,0x89,0xf8]
+; CHECK-NEXT:    retq # encoding: [0xc3]
+  %shr = lshr i64 %x, 36
+  %and = and i64 %shr, 268435440
+  ret i64 %and
+}
+
+; The immediate (0x0ffffffffffffff0) can be made into an i8 by making it negative.
+
+define i64 @lopped64_64to8(i64 %x) {
+; CHECK-LABEL: lopped64_64to8:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    shrq $4, %rdi # encoding: [0x48,0xc1,0xef,0x04]
+; CHECK-NEXT:    movabsq $1152921504606846960, %rax # encoding: [0x48,0xb8,0xf0,0xff,0xff,0xff,0xff,0xff,0xff,0x0f]
+; CHECK-NEXT:    # imm = 0xFFFFFFFFFFFFFF0
+; CHECK-NEXT:    andq %rdi, %rax # encoding: [0x48,0x21,0xf8]
+; CHECK-NEXT:    retq # encoding: [0xc3]
+  %shr = lshr i64 %x, 4
+  %and = and i64 %shr, 1152921504606846960
+  ret i64 %and
+}
+
+; The immediate (0x0ffffffffff0fff0) can be made into an i32 by making it negative.
+
+define i64 @lopped64_64to32(i64 %x) {
+; CHECK-LABEL: lopped64_64to32:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    shrq $4, %rdi # encoding: [0x48,0xc1,0xef,0x04]
+; CHECK-NEXT:    movabsq $1152921504605863920, %rax # encoding: [0x48,0xb8,0xf0,0xff,0xf0,0xff,0xff,0xff,0xff,0x0f]
+; CHECK-NEXT:    # imm = 0xFFFFFFFFFF0FFF0
+; CHECK-NEXT:    andq %rdi, %rax # encoding: [0x48,0x21,0xf8]
+; CHECK-NEXT:    retq # encoding: [0xc3]
+  %shr = lshr i64 %x, 4
+  %and = and i64 %shr, 1152921504605863920
+  ret i64 %and
+}
+
+; The transform is not limited to shifts - computeKnownBits() knows the top 4 bits
+; must be cleared, so 0x0fffff80 can become 0x80 sign-extended.
+
+define i32 @shrinkAndKnownBits(i32 %x) {
+; CHECK-LABEL: shrinkAndKnownBits:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movl %edi, %ecx # encoding: [0x89,0xf9]
+; CHECK-NEXT:    movl $4042322161, %eax # encoding: [0xb8,0xf1,0xf0,0xf0,0xf0]
+; CHECK-NEXT:    # imm = 0xF0F0F0F1
+; CHECK-NEXT:    imulq %rcx, %rax # encoding: [0x48,0x0f,0xaf,0xc1]
+; CHECK-NEXT:    shrq $36, %rax # encoding: [0x48,0xc1,0xe8,0x24]
+; CHECK-NEXT:    andl $268435328, %eax # encoding: [0x25,0x80,0xff,0xff,0x0f]
+; CHECK-NEXT:    # imm = 0xFFFFF80
+; CHECK-NEXT:    # kill: def %eax killed %eax killed %rax
+; CHECK-NEXT:    retq # encoding: [0xc3]
+  %div = udiv i32 %x, 17
+  %and = and i32 %div, 268435328
+  ret i32 %and
+}
+