[X86] Enable the add with 128 -> sub with -128 encoding trick with X86ISD::ADD when the carry flag isn't used.

This allows us to use an 8-bit sign extended immediate instead of a 16 or 32 bit immediate.

Also do similar for 0x80000000 with 64-bit adds to avoid having to use a movabsq.

llvm-svn: 355485

llvm/lib/Target/X86/X86InstrCompiler.td

@@ -1491,6 +1491,13 @@ def : Pat<(add GR64:$src1, 128),
 def : Pat<(store (add (loadi64 addr:$dst), 128), addr:$dst),
           (SUB64mi8 addr:$dst, -128)>;
 
+def : Pat<(X86add_flag_nocf GR16:$src1, 128),
+          (SUB16ri8 GR16:$src1, -128)>;
+def : Pat<(X86add_flag_nocf GR32:$src1, 128),
+          (SUB32ri8 GR32:$src1, -128)>;
+def : Pat<(X86add_flag_nocf GR64:$src1, 128),
+          (SUB64ri8 GR64:$src1, -128)>;
+
 // The same trick applies for 32-bit immediate fields in 64-bit
 // instructions.
 def : Pat<(add GR64:$src1, 0x0000000080000000),
@@ -1498,6 +1505,9 @@ def : Pat<(add GR64:$src1, 0x0000000080000000),
 def : Pat<(store (add (loadi64 addr:$dst), 0x0000000080000000), addr:$dst),
           (SUB64mi32 addr:$dst, 0xffffffff80000000)>;
 
+def : Pat<(X86add_flag_nocf GR64:$src1, 0x0000000080000000),
+          (SUB64ri32 GR64:$src1, 0xffffffff80000000)>;
+
 // To avoid needing to materialize an immediate in a register, use a 32-bit and
 // with implicit zero-extension instead of a 64-bit and if the immediate has at
 // least 32 bits of leading zeros. If in addition the last 32 bits can be

llvm/test/CodeGen/X86/add.ll

@@ -507,3 +507,156 @@ define i32 @add_to_sub(i32 %a, i32 %b) {
   %r = add i32 %add, 1
   ret i32 %r
 }
+
+declare void @bar_i32(i32)
+declare void @bar_i64(i64)
+
+; Make sure we can use sub -128 for add 128 when the flags are used.
+define void @add_i32_128_flag(i32 %x) {
+; X32-LABEL: add_i32_128_flag:
+; X32:       # %bb.0: # %entry
+; X32-NEXT:    movl $128, %eax
+; X32-NEXT:    addl {{[0-9]+}}(%esp), %eax
+; X32-NEXT:    je .LBB17_2
+; X32-NEXT:  # %bb.1: # %if.then
+; X32-NEXT:    pushl %eax
+; X32-NEXT:    .cfi_adjust_cfa_offset 4
+; X32-NEXT:    calll bar_i32
+; X32-NEXT:    addl $4, %esp
+; X32-NEXT:    .cfi_adjust_cfa_offset -4
+; X32-NEXT:  .LBB17_2: # %if.end
+; X32-NEXT:    retl
+;
+; X64-LINUX-LABEL: add_i32_128_flag:
+; X64-LINUX:       # %bb.0: # %entry
+; X64-LINUX-NEXT:    subl $-128, %edi
+; X64-LINUX-NEXT:    je .LBB17_1
+; X64-LINUX-NEXT:  # %bb.2: # %if.then
+; X64-LINUX-NEXT:    jmp bar_i32 # TAILCALL
+; X64-LINUX-NEXT:  .LBB17_1: # %if.end
+; X64-LINUX-NEXT:    retq
+;
+; X64-WIN32-LABEL: add_i32_128_flag:
+; X64-WIN32:       # %bb.0: # %entry
+; X64-WIN32-NEXT:    subl $-128, %ecx
+; X64-WIN32-NEXT:    je .LBB17_1
+; X64-WIN32-NEXT:  # %bb.2: # %if.then
+; X64-WIN32-NEXT:    jmp bar_i32 # TAILCALL
+; X64-WIN32-NEXT:  .LBB17_1: # %if.end
+; X64-WIN32-NEXT:    retq
+entry:
+  %add = add i32 %x, 128
+  %tobool = icmp eq i32 %add, 0
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:
+  tail call void @bar_i32(i32 %add)
+  br label %if.end
+
+if.end:
+  ret void
+}
+
+; Make sure we can use sub -128 for add 128 when the flags are used.
+define void @add_i64_128_flag(i64 %x) {
+; X32-LABEL: add_i64_128_flag:
+; X32:       # %bb.0: # %entry
+; X32-NEXT:    movl {{[0-9]+}}(%esp), %ecx
+; X32-NEXT:    movl $128, %eax
+; X32-NEXT:    addl {{[0-9]+}}(%esp), %eax
+; X32-NEXT:    adcl $0, %ecx
+; X32-NEXT:    movl %eax, %edx
+; X32-NEXT:    orl %ecx, %edx
+; X32-NEXT:    je .LBB18_2
+; X32-NEXT:  # %bb.1: # %if.then
+; X32-NEXT:    pushl %ecx
+; X32-NEXT:    .cfi_adjust_cfa_offset 4
+; X32-NEXT:    pushl %eax
+; X32-NEXT:    .cfi_adjust_cfa_offset 4
+; X32-NEXT:    calll bar_i64
+; X32-NEXT:    addl $8, %esp
+; X32-NEXT:    .cfi_adjust_cfa_offset -8
+; X32-NEXT:  .LBB18_2: # %if.end
+; X32-NEXT:    retl
+;
+; X64-LINUX-LABEL: add_i64_128_flag:
+; X64-LINUX:       # %bb.0: # %entry
+; X64-LINUX-NEXT:    subq $-128, %rdi
+; X64-LINUX-NEXT:    je .LBB18_1
+; X64-LINUX-NEXT:  # %bb.2: # %if.then
+; X64-LINUX-NEXT:    jmp bar_i64 # TAILCALL
+; X64-LINUX-NEXT:  .LBB18_1: # %if.end
+; X64-LINUX-NEXT:    retq
+;
+; X64-WIN32-LABEL: add_i64_128_flag:
+; X64-WIN32:       # %bb.0: # %entry
+; X64-WIN32-NEXT:    subq $-128, %rcx
+; X64-WIN32-NEXT:    je .LBB18_1
+; X64-WIN32-NEXT:  # %bb.2: # %if.then
+; X64-WIN32-NEXT:    jmp bar_i64 # TAILCALL
+; X64-WIN32-NEXT:  .LBB18_1: # %if.end
+; X64-WIN32-NEXT:    retq
+entry:
+  %add = add i64 %x, 128
+  %tobool = icmp eq i64 %add, 0
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:
+  tail call void @bar_i64(i64 %add)
+  br label %if.end
+
+if.end:
+  ret void
+}
+
+; Make sure we can use sub -2147483648 for add 2147483648 when the flags are used.
+define void @add_i64_2147483648_flag(i64 %x) {
+; X32-LABEL: add_i64_2147483648_flag:
+; X32:       # %bb.0: # %entry
+; X32-NEXT:    movl {{[0-9]+}}(%esp), %ecx
+; X32-NEXT:    movl $-2147483648, %eax # imm = 0x80000000
+; X32-NEXT:    addl {{[0-9]+}}(%esp), %eax
+; X32-NEXT:    adcl $0, %ecx
+; X32-NEXT:    movl %eax, %edx
+; X32-NEXT:    orl %ecx, %edx
+; X32-NEXT:    je .LBB19_2
+; X32-NEXT:  # %bb.1: # %if.then
+; X32-NEXT:    pushl %ecx
+; X32-NEXT:    .cfi_adjust_cfa_offset 4
+; X32-NEXT:    pushl %eax
+; X32-NEXT:    .cfi_adjust_cfa_offset 4
+; X32-NEXT:    calll bar_i64
+; X32-NEXT:    addl $8, %esp
+; X32-NEXT:    .cfi_adjust_cfa_offset -8
+; X32-NEXT:  .LBB19_2: # %if.end
+; X32-NEXT:    retl
+;
+; X64-LINUX-LABEL: add_i64_2147483648_flag:
+; X64-LINUX:       # %bb.0: # %entry
+; X64-LINUX-NEXT:    subq $-2147483648, %rdi # imm = 0x80000000
+; X64-LINUX-NEXT:    je .LBB19_1
+; X64-LINUX-NEXT:  # %bb.2: # %if.then
+; X64-LINUX-NEXT:    jmp bar_i64 # TAILCALL
+; X64-LINUX-NEXT:  .LBB19_1: # %if.end
+; X64-LINUX-NEXT:    retq
+;
+; X64-WIN32-LABEL: add_i64_2147483648_flag:
+; X64-WIN32:       # %bb.0: # %entry
+; X64-WIN32-NEXT:    subq $-2147483648, %rcx # imm = 0x80000000
+; X64-WIN32-NEXT:    je .LBB19_1
+; X64-WIN32-NEXT:  # %bb.2: # %if.then
+; X64-WIN32-NEXT:    jmp bar_i64 # TAILCALL
+; X64-WIN32-NEXT:  .LBB19_1: # %if.end
+; X64-WIN32-NEXT:    retq
+entry:
+  %add = add i64 %x, 2147483648
+  %tobool = icmp eq i64 %add, 0
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:
+  tail call void @bar_i64(i64 %add)
+  br label %if.end
+
+if.end:
+  ret void
+}

llvm/test/CodeGen/X86/xaluo.ll

@@ -293,10 +293,9 @@ define zeroext i1 @saddoi64imm4(i64 %v1, i64* %res) {
 define zeroext i1 @saddoi64imm5(i64 %v1, i64* %res) {
 ; SDAG-LABEL: saddoi64imm5:
 ; SDAG:       ## %bb.0:
-; SDAG-NEXT:    movl $2147483648, %ecx ## imm = 0x80000000
+; SDAG-NEXT:    subq $-2147483648, %rdi ## imm = 0x80000000
-; SDAG-NEXT:    addq %rdi, %rcx
 ; SDAG-NEXT:    seto %al
-; SDAG-NEXT:    movq %rcx, (%rsi)
+; SDAG-NEXT:    movq %rdi, (%rsi)
 ; SDAG-NEXT:    retq
 ;
 ; FAST-LABEL: saddoi64imm5: