Index: llvm/include/llvm/CodeGen/CommandFlags.inc
===================================================================
--- llvm/include/llvm/CodeGen/CommandFlags.inc
+++ llvm/include/llvm/CodeGen/CommandFlags.inc
@@ -151,18 +151,27 @@
                                     "attribute not to use exceptions"),
                            cl::init(false));
 
+static const auto DenormFlagEnumOptions =
+  cl::values(clEnumValN(DenormalMode::IEEE, "ieee",
+                        "IEEE 754 denormal numbers"),
+             clEnumValN(DenormalMode::PreserveSign, "preserve-sign",
+                        "the sign of a  flushed-to-zero number is preserved "
+                        "in the sign of 0"),
+             clEnumValN(DenormalMode::PositiveZero, "positive-zero",
+                        "denormals are flushed to positive zero"));
+
 // FIXME: Doesn't have way to specify separate input and output modes.
 static cl::opt<DenormalMode::DenormalModeKind> DenormalFPMath(
     "denormal-fp-math",
     cl::desc("Select which denormal numbers the code is permitted to require"),
     cl::init(DenormalMode::IEEE),
-    cl::values(clEnumValN(DenormalMode::IEEE, "ieee",
-                          "IEEE 754 denormal numbers"),
-               clEnumValN(DenormalMode::PreserveSign, "preserve-sign",
-                          "the sign of a  flushed-to-zero number is preserved "
-                          "in the sign of 0"),
-               clEnumValN(DenormalMode::PositiveZero, "positive-zero",
-                          "denormals are flushed to positive zero")));
+    DenormFlagEnumOptions);
+
+static cl::opt<DenormalMode::DenormalModeKind> DenormalFP32Math(
+    "denormal-fp-math-f32",
+    cl::desc("Select which denormal numbers the code is permitted to require for float"),
+    cl::init(DenormalMode::Invalid),
+    DenormFlagEnumOptions);
 
 static cl::opt<bool> EnableHonorSignDependentRoundingFPMath(
     "enable-sign-dependent-rounding-fp-math", cl::Hidden,
@@ -430,6 +439,21 @@
   HANDLE_BOOL_ATTR(EnableNoNaNsFPMath, "no-nans-fp-math");
   HANDLE_BOOL_ATTR(EnableNoSignedZerosFPMath, "no-signed-zeros-fp-math");
 
+  if (DenormalFPMath.getNumOccurrences() > 0 &&
+      !F.hasFnAttribute("denormal-fp-math")) {
+    // FIXME: Command line flag should expose separate input/output modes.
+    NewAttrs.addAttribute("denormal-fp-math",
+                          DenormalMode(DenormalFPMath, DenormalFPMath).str());
+  }
+
+  if (DenormalFP32Math.getNumOccurrences() > 0 &&
+      !F.hasFnAttribute("denormal-fp-math-f32")) {
+    // FIXME: Command line flag should expose separate input/output modes.
+    NewAttrs.addAttribute(
+      "denormal-fp-math-f32",
+      DenormalMode(DenormalFP32Math, DenormalFP32Math).str());
+  }
+
   if (TrapFuncName.getNumOccurrences() > 0)
     for (auto &B : F)
       for (auto &I : B)
Index: llvm/lib/Target/TargetMachine.cpp
===================================================================
--- llvm/lib/Target/TargetMachine.cpp
+++ llvm/lib/Target/TargetMachine.cpp
@@ -64,12 +64,12 @@
   RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
   RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math");
 
-  Options.setFP32DenormalMode(DenormalMode::getInvalid());
   if (F.hasFnAttribute("denormal-fp-math-f32")) {
     Options.setFPDenormalMode(
       parseDenormalFPAttribute(
         F.getFnAttribute("denormal-fp-math-f32").getValueAsString()));
-  }
+  } else
+    Options.setFP32DenormalMode(DefaultOptions.getRawFP32DenormalMode());
 
   if (F.hasFnAttribute("denormal-fp-math")) {
     Options.setFPDenormalMode(
Index: llvm/test/Other/opt-override-denormal-fp-math-f32.ll
===================================================================
--- /dev/null
+++ llvm/test/Other/opt-override-denormal-fp-math-f32.ll
@@ -0,0 +1,23 @@
+; RUN: opt -S -denormal-fp-math-f32=ieee %s | FileCheck -check-prefixes=IEEE,ALL %s
+; RUN: opt -S -denormal-fp-math-f32=preserve-sign %s | FileCheck -check-prefixes=PRESERVESIGN,ALL %s
+; RUN: opt -S -denormal-fp-math-f32=positive-zero %s | FileCheck -check-prefixes=POSZERO,ALL %s
+
+; ALL: @no_denormal_fp_math_f32_attr() [[NOATTR:#[0-9]+]] {
+define i32 @no_denormal_fp_math_f32_attr() #0 {
+entry:
+  ret i32 0
+}
+
+; ALL: denormal_fp_math_attr_preserve_sign_ieee() [[ATTR:#[0-9]+]] {
+define i32 @denormal_fp_math_attr_preserve_sign_ieee() #1 {
+entry:
+  ret i32 0
+}
+
+; ALL-DAG: attributes [[ATTR]] = { nounwind "denormal-fp-math-f32"="preserve-sign,ieee" }
+; IEEE-DAG: attributes [[NOATTR]] = { nounwind "denormal-fp-math-f32"="ieee,ieee" }
+; PRESERVESIGN-DAG: attributes [[NOATTR]] = { nounwind "denormal-fp-math-f32"="preserve-sign,preserve-sign" }
+; POSITIVEZERO-DAG: attributes [[NOATTR]] = { nounwind "denormal-fp-math-f32"="positive-zero,positive-zero" }
+
+attributes #0 = { nounwind }
+attributes #1 = { nounwind "denormal-fp-math-f32"="preserve-sign,ieee" }
Index: llvm/test/Other/opt-override-denormal-fp-math.ll
===================================================================
--- /dev/null
+++ llvm/test/Other/opt-override-denormal-fp-math.ll
@@ -0,0 +1,23 @@
+; RUN: opt -S -denormal-fp-math=ieee %s | FileCheck -check-prefixes=IEEE,ALL %s
+; RUN: opt -S -denormal-fp-math=preserve-sign %s | FileCheck -check-prefixes=PRESERVESIGN,ALL %s
+; RUN: opt -S -denormal-fp-math=positive-zero %s | FileCheck -check-prefixes=POSZERO,ALL %s
+
+; ALL: @no_denormal_fp_math_attr() [[NOATTR:#[0-9]+]] {
+define i32 @no_denormal_fp_math_attr() #0 {
+entry:
+  ret i32 0
+}
+
+; ALL: denormal_fp_math_attr_preserve_sign_ieee() [[ATTR:#[0-9]+]] {
+define i32 @denormal_fp_math_attr_preserve_sign_ieee() #1 {
+entry:
+  ret i32 0
+}
+
+; ALL-DAG: attributes [[ATTR]] = { nounwind "denormal-fp-math"="preserve-sign,ieee" }
+; IEEE-DAG: attributes [[NOATTR]] = { nounwind "denormal-fp-math"="ieee,ieee" }
+; PRESERVESIGN-DAG: attributes [[NOATTR]] = { nounwind "denormal-fp-math"="preserve-sign,preserve-sign" }
+; POSITIVEZERO-DAG: attributes [[NOATTR]] = { nounwind "denormal-fp-math"="positive-zero,positive-zero" }
+
+attributes #0 = { nounwind }
+attributes #1 = { nounwind "denormal-fp-math"="preserve-sign,ieee" }